LeetCode

R.I.P. to my old Leetcode repository, where there were 5.7k+ stars and 2.2k+ forks (ever the top 3 in the field).
Since free questions may be even mistakenly taken down by some companies, only solutions will be post on now.
There are new LeetCode questions every week. I'll keep updating for full summary and better solutions.
For more problem solutions, you can see my LintCode, GoogleKickStart, GoogleCodeJamIO repositories.
For more challenging problem solutions, you can also see my GoogleCodeJam, FacebookHackerCup repositories.
Hope you enjoy the journey of learning data structures and algorithms.
Notes: "🔒" means your subscription of LeetCode premium membership is required for reading the question.

Solutions

0001 - 1000

Algorithms

Database

SQL

Shell

Shell Script

Reference

C++
Python
- Time Complexity
Algorithms
Math
- Stack Exchange
Visualization
Handy Table
- Thinking Techniques as follows:

n	Complexity	Possible Algorithms & Techniques
10¹⁸+	O(1)	Math
10¹⁸	O(logn)	Binary & Ternary Search / Matrix Power / Cycle Tricks / Big Simulation Steps / Values Reranking / Math
10¹⁶	O(n^1/2)	Math
10⁸	O(n)	Greedy / Ad-hoc / DP
4×10⁷	O(nlogn)	Linear # Calls to Binary & Ternary Search / Pre-processing & Querying / Divide and Conquer
10⁴	O(n²)	Ad-hoc / DP / Greedy / Divide and Conquer / Branch and Bound
500	O(n³)	Ad-hoc / DP / Greedy / Divide and Conquer / Branch and Bound
90	O(n⁴)	Ad-hoc / DP / Greedy / Divide and Conquer / Branch and Bound
50	O(n⁵)	Branch and Bound
40	O(n×2^n/2)	Meet in the Middle
20	O(n×2ⁿ)	Backtracking / Generating 2ⁿ Subsets / Bitmask Technique
11	O(n!)	Factorial / Permutation / Combination Algorithm

Bit Manipulation

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1310	XOR Queries of a Subarray	C++ Python	O(n)	O(1)	Medium
1318	Minimum Flips to Make a OR b Equal to c	C++ Python	O(1)	O(1)	Medium
1342	Number of Steps to Reduce a Number to Zero	C++ Python	O(logn)	O(1)	Easy
1558	Minimum Numbers of Function Calls to Make Target Array	C++ Python	O(nlogn)	O(1)	Medium		Greedy
1707	Maximum XOR With an Element From Array	C++ Python	O(nlogn + mlogm + nlogk + mlogk)	O(nlogk)	Hard	variant of Maximum XOR of Two Numbers in an Array	Greedy, Trie
1720	Decode XORed Array	C++ Python	O(n)	O(1)	Easy
1734	Decode XORed Permutation	C++ Python	O(n)	O(1)	Medium
1829	Maximum XOR for Each Query	C++ Python	O(n)	O(1)	Medium
2151	Maximum Good People Based on Statements	C++ Python	O(n^2 2^n)*	O(1)	Hard		Bitmasks, Brute Force
2212	Maximum Points in an Archery Competition	C++ Python	O(n 2^n)*	O(n)	Medium		Bitmasks, Brute Force
2220	Minimum Bit Flips to Convert Number	C++ Python	O(logn)	O(1)	Easy		Bit Manipulation
2275	Largest Combination With Bitwise AND Greater Than Zero	C++ Python	O(nlogr)	O(logr)	Medium		Bit Manipulation, Freq Table

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Array

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1002	Find Common Characters	C++ Python	O(n l)*	O(1)	Easy
1007	Minimum Domino Rotations For Equal Row	C++ Python	O(n)	O(1)	Medium
1010	Pairs of Songs With Total Durations Divisible by 60	C++ Python	O(n)	O(1)	Easy
1013	Partition Array Into Three Parts With Equal Sum	C++ Python	O(n)	O(1)	Easy
1014	Best Sightseeing Pair	C++ Python	O(n)	O(1)	Medium
1018	Binary Prefix Divisible By 5	C++ Python	O(n)	O(1)	Easy
1030	Matrix Cells in Distance Order	C++ Python	O(m n)*	O(1)	Easy
1031	Maximum Sum of Two Non-Overlapping Subarrays	C++ Python	O(n)	O(1)	Medium
1051	Height Checker	C++ Python	O(nlogn)	O(n)	Easy
1052	Grumpy Bookstore Owner	C++ Python	O(n)	O(1)	Medium
1072	Flip Columns For Maximum Number of Equal Rows	C++ Python	O(m n)*	O(m n)*	Medium
1074	Number of Submatrices That Sum to Target	C++ Python	O(m^2 n)*	O(n)	Hard
1085	Sum of Digits in the Minimum Number	C++ Python	O(n l)*	O(l)	Easy	🔒
1089	Duplicate Zeros	C++ Python	O(n)	O(1)	Easy
1093	Statistics from a Large Sample	C++ Python	O(n)	O(1)	Medium
1099	Two Sum Less Than K	C++ Python	O(nlogn)	O(1)	Easy	🔒
1109	Corporate Flight Bookings	C++ Python	O(n)	O(1)	Medium		Line Sweep
1144	Decrease Elements To Make Array Zigzag	C++ Python	O(n)	O(1)	Medium
1184	Distance Between Bus Stops	C++ Python	O(n)	O(1)	Easy
1200	Minimum Absolute Difference	C++ Python	O(nlogn)	O(n)	Easy
1222	Queens That Can Attack the King	C++ Python	O(1)	O(1)	Medium
1252	Cells with Odd Values in a Matrix	C++ Python	O(n + m)	O(n + m)	Easy
1260	Shift 2D Grid	C++ Python	O(n)	O(1)	Easy
1267	Count Servers that Communicate	C++ Python	O(m n)*	O(m + n)	Medium
1275	Find Winner on a Tic Tac Toe Game	C++ Python	O(1)	O(1)	Easy
1295	Find Numbers with Even Number of Digits	C++ Python	O(nlog(logm))	O(logm)	Easy
1299	Replace Elements with Greatest Element on Right Side	C++ Python	O(n)	O(1)	Easy
1304	Find N Unique Integers Sum up to Zero	C++ Python	O(n)	O(1)	Easy
1313	Decompress Run-Length Encoded List	C++ Python	O(n)	O(1)	Easy
1329	Sort the Matrix Diagonally	C++ Python	O(m n * log(min(m, n))*	O(m n)*	Medium		Sort
1331	Rank Transform of an Array	C++ Python	O(nlogn)	O(n)	Easy
1333	Filter Restaurants by Vegan-Friendly, Price and Distance	C++ Python	O(rlogr)	O(r)	Medium		Sort
1337	The K Weakest Rows in a Matrix	C++ Python	O(m n)*	O(k)	Easy		OrderedDict, Quick Select
1343	Number of Sub-arrays of Size K and Average Greater than or Equal to Threshold	C++ Python	O(n)	O(1)	Medium
1346	Check If N and Its Double Exist	C++ Python	O(n)	O(n)	Easy
1351	Count Negative Numbers in a Sorted Matrix	C++ Python	O(m + n)	O(1)	Easy
1375	Bulb Switcher III	C++ Python	O(n)	O(1)	Medium
1380	Lucky Numbers in a Matrix	C++ Python	O(m n)*	O(m + n)	Easy
1389	Create Target Array in the Given Order	C++ Python	O(n^2)	O(1)	Easy
1394	Find Lucky Integer in an Array	C++ Python	O(n)	O(n)	Easy
1399	Count Largest Group	C++ Python	O(nlogn)	O(n)	Easy
1404	Number of Steps to Reduce a Number in Binary Representation to One	C++ Python	O(n)	O(1)	Medium
1413	Minimum Value to Get Positive Step by Step Sum	C++ Python	O(n)	O(1)	Easy
1426	Counting Elements	C++ Python	O(n)	O(n)	Easy	🔒
1427	Perform String Shifts	C++ Python	O(n + l)	O(1)	Easy	🔒
1428	Leftmost Column with at Least a One	C++ Python	O(m + n)	O(1)	Medium	🔒
1431	Kids With the Greatest Number of Candies	C++ Python	O(n)	O(1)	Easy
1437	Check If All 1's Are at Least Length K Places Away	C++ Python	O(n)	O(1)	Medium
1450	Number of Students Doing Homework at a Given Time	C++ Python	O(n)	O(1)	Easy
1460	Make Two Arrays Equal by Reversing Sub-arrays	C++ Python	O(n)	O(n)	Easy
1464	Maximum Product of Two Elements in an Array	C++ Python	O(n)	O(1)	Easy
1465	Maximum Area of a Piece of Cake After Horizontal and Vertical Cuts	C++ Python	O(hlogh + wlogw)	O(1)	Medium
1470	Shuffle the Array	C++ Python	O(n)	O(1)	Easy		Inplace
1471	The k Strongest Values in an Array	C++ Python	O(n)	O(1)	Medium		Quick Select
1475	Final Prices With a Special Discount in a Shop	C++ Python	O(n)	O(n)	Easy		Mono Stack
1480	Running Sum of 1d Array	C++ Python	O(n)	O(1)	Easy
1491	Average Salary Excluding the Minimum and Maximum Salary	C++ Python	O(n)	O(1)	Easy
1502	Can Make Arithmetic Progression From Sequence	C++ Python	O(n)	O(1)	Easy
1503	Last Moment Before All Ants Fall Out of a Plank	C++ Python	O(n)	O(1)	Medium
1534	Count Good Triplets	C++ Python	O(n^3)	O(1)	Easy
1535	Find the Winner of an Array Game	C++ Python	O(n)	O(1)	Medium
1538	Guess the Majority in a Hidden Array	C++ Python	O(n)	O(1)	Medium	🔒
1550	Three Consecutive Odds	C++ Python	O(n)	O(1)	Easy
1559	Detect Cycles in 2D Grid	C++ Python	O(m n)*	O(m n)*	Hard		Union Find, BFS
1560	Most Visited Sector in a Circular Track	C++ Python	O(n)	O(1)	Easy
1562	Find Latest Group of Size M	C++ Python	O(n)	O(n)	Medium
1566	Detect Pattern of Length M Repeated K or More Times	C++ Python	O(n)	O(1)	Easy
1572	Matrix Diagonal Sum	C++ Python	O(n)	O(1)	Easy
1574	Shortest Subarray to be Removed to Make Array Sorted	C++ Python	O(n)	O(1)	Medium
1582	Special Positions in a Binary Matrix	C++ Python	O(n^2)	O(n)	Easy
1583	Count Unhappy Friends	C++ Python	O(n^2)	O(n^2)	Medium
1619	Mean of Array After Removing Some Elements	C++ Python	O(n)	O(1)	Easy		Quick Select
1629	Slowest Key	C++ Python	O(n)	O(1)	Easy
1646	Get Maximum in Generated Array	C++ Python	O(n)	O(n)	Easy
1652	Defuse the Bomb	C++ Python	O(n)	O(1)	Easy
1672	Richest Customer Wealth	C++ Python	O(m n)*	O(1)	Easy
1700	Number of Students Unable to Eat Lunch	C++ Python	O(n)	O(1)	Easy
1701	Average Waiting Time	C++ Python	O(n)	O(1)	Medium
1706	Where Will the Ball Fall	C++ Python	O(m n)*	O(1)	Medium
1714	Sum Of Special Evenly-Spaced Elements In Array	C++ Python	O(n sqrt(n))*	O(n sqrt(n))*	Hard	🔒
1726	Tuple with Same Product	C++ Python	O(n^2)	O(n^2)	Medium
1732	Find the Highest Altitude	C++ Python	O(n)	O(1)	Medium
1738	Find Kth Largest XOR Coordinate Value	C++ Python	O(m n)* on average	O(m n)*	Medium		Quick Select
1742	Maximum Number of Balls in a Box	C++ Python	O(nlogm)	O(logm)	Easy
1752	Check if Array Is Sorted and Rotated	C++ Python	O(n)	O(1)	Easy
1755	Closest Subsequence Sum	C++ Python	O(n 2^(n/2))*	O(2^(n/2))	Hard		Meet in the Middle
1773	Count Items Matching a Rule	C++ Python	O(n)	O(1)	Easy
1779	Find Nearest Point That Has the Same X or Y Coordinate	C++ Python	O(n)	O(1)	Easy
1800	Maximum Ascending Subarray Sum	C++ Python	O(n)	O(1)	Easy
1826	Faulty Sensor	C++ Python	O(n)	O(1)	Easy	🔒
1848	Minimum Distance to the Target Element	C++ Python	O(n)	O(1)	Easy
1861	Rotating the Box	C++ Python	O(m n)*	O(1)	Medium
1869	Longer Contiguous Segments of Ones than Zeros	C++ Python	O(n)	O(1)	Easy
1878	Get Biggest Three Rhombus Sums in a Grid	C++ Python	O(m n * min(m, n))*	O(m n)*	Easy
1886	Determine Whether Matrix Can Be Obtained By Rotation	C++ Python	O(m n)*	O(1)	Easy
1895	Largest Magic Square	C++ Python	O(max(m, n) min(m, n)^3)*	O(m n)*	Medium
1906	Minimum Absolute Difference Queries	C++ Python	O(r (n + q))*	O(r n)*	Medium		Prefix Sum, Binary Search
1909	Remove One Element to Make the Array Strictly Increasing	C++ Python	O(n)	O(1)	Easy
1914	Cyclically Rotating a Grid	C++ Python	O(m n)*	O(1)	Medium		Inplace
1920	Build Array from Permutation	C++ Python	O(n)	O(1)	Easy		Inplace
1929	Concatenation of Array	C++ Python	O(n)	O(1)	Easy
1940	Longest Common Subsequence Between Sorted Arrays	C++ Python	O(m n)*	O(l)	Medium	🔒
1958	Check if Move is Legal	C++ Python	O(1)	O(1)	Medium
1966	Binary Searchable Numbers in an Unsorted Array	C++ Python	O(n)	O(n)	Medium	🔒	Prefix Sum
1970	Last Day Where You Can Still Cross	C++ Python	O(m n)*	O(m n)*	Hard	variant of Bricks Falling When Hit	Union Find
1983	Widest Pair of Indices With Equal Range Sum	C++ Python	O(n)	O(n)	Medium	variant of Find the Longest Substring Containing Vowels in Even Counts, 🔒	Prefix Sum
1991	Find the Middle Index in Array	C++ Python	O(n)	O(1)	Easy		Prefix Sum
1992	Find All Groups of Farmland	C++ Python	O(m n)*	O(1)	Medium	variant of Number of Islands
1998	GCD Sort of an Array	C++ Python	O(nlogn + m)	O(n + m)	Hard		Union Find, `Sieve of Eratosthenes`
2007	Find Original Array From Doubled Array	C++ Python	O(n + klogk)	O(k)	Medium	variant of Array of Doubled Pairs
2011	Final Value of Variable After Performing Operations	C++ Python	O(n)	O(1)	Easy
2012	Sum of Beauty in the Array	C++ Python	O(n)	O(n)	Medium		Prefix Sum
2016	Maximum Difference Between Increasing Elements	C++ Python	O(n)	O(1)	Easy	variant of Best Time to Buy and Sell Stock
2017	Grid Game	C++ Python	O(n)	O(1)	Medium		Prefix Sum
2018	Check if Word Can Be Placed In Crossword	C++ Python	O(m n)*	O(1)	Medium
2022	Convert 1D Array Into 2D Array	C++ Python	O(m n)*	O(1)	Easy
2033	Minimum Operations to Make a Uni-Value Grid	C++ Python	O(m n)* on average	O(m n)*	Medium	variant of Minimum Moves to Equal Array Elements II	Math, Median, Quick Select
2035	Partition Array Into Two Arrays to Minimize Sum Difference	C++ Python	O(n 2^n)*	O(2^n)	Hard		Meet in the Middle
2038	Remove Colored Pieces if Both Neighbors are the Same Color	C++ Python	O(n)	O(1)	Medium
2055	Plates Between Candles	C++ Python	O(n + q)	O(n)	Medium		Prefix Sum
2057	Smallest Index With Equal Value	C++ Python	O(n)	O(1)	Easy
2075	Decode the Slanted Ciphertext	C++ Python	O(n)	O(1)	Medium
2078	Two Furthest Houses With Different Colors	C++ Python	O(n)	O(1)	Easy
2079	Watering Plants	C++ Python	O(n)	O(1)	Medium
2098	Subsequence of Size K With the Largest Even Sum	C++ Python	O(n) on average	O(1)	Medium	🔒	Quick Select
2099	Find Subsequence of Length K With the Largest Sum	C++ Python	O(n) on average	O(n)	Easy		Quick Select
2100	Find Good Days to Rob the Bank	C++ Python	O(n)	O(n)	Medium		Prefix Sum
2106	Maximum Fruits Harvested After at Most K Steps	C++ Python	O(n)	O(n)	Hard		Prefix Sum
2113	Elements in Array After Removing and Replacing Elements	C++ Python	O(n)	O(1)	Medium	🔒
2121	Intervals Between Identical Elements	C++ Python	O(n)	O(n)	Medium		Prefix Sum
2122	Recover the Original Array	C++ Python	O(n^2)	O(n)	Hard
2128	Remove All Ones With Row and Column Flips	C++ Python	O(m n)*	O(1)	Medium	🔒
2132	Stamping the Grid	C++ Python	O(m n)*	O(m n)*	Hard		Prefix Sum
2155	All Divisions With the Highest Score of a Binary Array	C++ Python	O(n)	O(1)	Medium		Prefix Sum
2194	Cells in a Range on an Excel Sheet	C++ Python	O(26^2)	O(1)	Easy
2202	Maximize the Topmost Element After K Moves	C++ Python	O(min(n, k))	O(1)	Medium		Constructive Algorithms
2210	Count Hills and Valleys in an Array	C++ Python	O(n)	O(1)	Easy		Simulation
2219	Maximum Sum Score of Array	C++ Python	O(n)	O(1)	Medium	🔒	Prefix Sum
2237	Count Positions on Street With Required Brightness	C++ Python	O(n + l)	O(min(n, l))	Medium	🔒	Line Sweep
2239	Find Closest Number to Zero	C++ Python	O(n)	O(1)	Easy		Array
2245	Maximum Trailing Zeros in a Cornered Path	C++ Python	O(m n)*	O(m n)*	Medium		Prefix Sum
2256	Minimum Average Difference	C++ Python	O(n)	O(1)	Medium		Prefix Sum
2270	Number of Ways to Split Array	C++ Python	O(n)	O(1)	Medium		Prefix Sum
2271	Maximum White Tiles Covered by a Carpet	C++ Python	O(nlogn)	O(1)	Medium		Sliding Window, Prefix Sum, Binary Search
2274	Maximum Consecutive Floors Without Special Floors	C++ Python	O(nlogn)	O(1)	Medium		Sort

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String

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1016	Binary String With Substrings Representing 1 To N	C++ Python	O(n^2)	O(1)	Medium
1023	Camelcase Matching	C++ Python	O(n l)*	O(1)	Medium
1061	Lexicographically Smallest Equivalent String	C++ Python	O(n)	O(n)	Medium	🔒	Union Find
1056	Confusing Number	C++ Python	O(logn)	O(logn)	Easy	🔒
1071	Greatest Common Divisor of Strings	C++ Python	O(m + n)	O(1)	Easy
1078	Occurrences After Bigram	C++ Python	O(n)	O(1)	Easy
1100	Find K-Length Substrings With No Repeated Characters	C++ Python	O(n)	O(k)	Medium	🔒
1108	Defanging an IP Address	C++ Python	O(n)	O(1)	Easy
1119	Remove Vowels from a String	C++ Python	O(n)	O(1)	Easy	🔒
1147	Longest Chunked Palindrome Decomposition	C++ Python	O(n)	O(1)	Hard		`Rabin-Karp Algorithm`
1177	Can Make Palindrome from Substring	C++ Python	O(m + n)	O(n)	Medium
1178	Number of Valid Words for Each Puzzle	C++ Python	O(n l + m * L)*	O(L!)	Hard		Trie, Bit Manipulation
1189	Maximum Number of Balloons	C++ Python	O(n)	O(1)	Easy		Hash
1233	Remove Sub-Folders from the Filesystem	C++ Python	O(n)	O(t)	Medium		Trie
1271	Hexspeak	C++ Python	O(n)	O(1)	Easy
1309	Decrypt String from Alphabet to Integer Mapping	C++ Python	O(n)	O(1)	Easy
1324	Print Words Vertically	C++ Python	O(n)	O(n)	Medium
1328	Break a Palindrome	C++ Python	O(n)	O(1)	Medium
1332	Remove Palindromic Subsequences	C++ Python	O(n)	O(1)	Easy
1347	Minimum Number of Steps to Make Two Strings Anagram	C++ Python	O(n)	O(1)	Medium
1370	Increasing Decreasing String	C++ Python	O(n)	O(1)	Easy		Sort
1371	Find the Longest Substring Containing Vowels in Even Counts	C++ Python	O(n)	O(1)	Medium
1374	Generate a String With Characters That Have Odd Count	C++ Python	O(n)	O(1)	Easy
1392	Longest Happy Prefix	C++ Python	O(n)	O(n)	Hard		`KMP Algorithm`, `Rabin-Karp Algorithm`
1408	String Matching in an Array	C++ Python	O(n)	O(t)	Easy		`KMP Algorithm`, `Aho-Corasick Automata`, Trie
1410	HTML Entity Parser	C++ Python	O(n)	O(t)	Medium		`Aho-Corasick Automata`, Trie
1417	Reformat The String	C++ Python	O(n)	O(1)	Easy
1422	Maximum Score After Splitting a String	C++ Python	O(n)	O(1)	Easy
1432	Max Difference You Can Get From Changing an Integer	C++ Python	O(logn)	O(logn)	Medium
1436	Destination City	C++ Python	O(n)	O(n)	Easy
1446	Consecutive Characters	C++ Python	O(n)	O(1)	Easy
1455	Check If a Word Occurs As a Prefix of Any Word in a Sentence	C++ Python	O(n)	O(n)	Easy		`KMP Algorithm`
1461	Check If a String Contains All Binary Codes of Size K	C++ Python	O(n k)*	O(k 2^k)*	Medium		Bit Manipulation
1496	Path Crossing	C++ Python	O(n)	O(n)	Easy
1507	Reformat Date	C++ Python	O(n)	O(1)	Easy
1528	Shuffle String	C++ Python	O(n)	O(1)	Easy
1529	Bulb Switcher IV	C++ Python	O(n)	O(1)	Medium
1540	Can Convert String in K Moves	C++ Python	O(n)	O(1)	Medium
1542	Find Longest Awesome Substring	C++ Python	O(n)	O(1)	Hard
1544	Make The String Great	C++ Python	O(n)	O(1)	Easy
1545	Find Kth Bit in Nth Binary String	C++ Python	O(n)	O(1)	Medium
1554	Strings Differ by One Character	C++ Python	O(n m)*	O(n)	Medium		`Rabin-Karp Algorithm`
1556	Thousand Separator	C++ Python	O(n)	O(1)	Easy
1573	Number of Ways to Split a String	C++ Python	O(n)	O(1)	Medium
1576	Replace All ?'s to Avoid Consecutive Repeating Characters	C++ Python	O(n)	O(1)	Easy
1592	Rearrange Spaces Between Words	C++ Python	O(n)	O(1)	Easy		Inplace
1598	Crawler Log Folder	C++ Python	O(n)	O(1)	Easy
1614	Maximum Nesting Depth of the Parentheses	C++ Python	O(n)	O(1)	Easy
1624	Largest Substring Between Two Equal Characters	C++ Python	O(n)	O(1)	Easy
1638	Count Substrings That Differ by One Character	C++ Python	O(m n)*	O(1)	Medium	variant of Count Unique Characters of All Substrings of a Given String	Tricky
1662	Check If Two String Arrays are Equivalent	C++ Python	O(n)	O(1)	Easy
1668	Maximum Repeating Substring	C++ Python	O(n)	O(m)	Easy		`KMP Algorithm`
1678	Goal Parser Interpretation	C++ Python	O(n)	O(1)	Easy
1684	Count the Number of Consistent Strings	C++ Python	O(n)	O(1)	Easy
1694	Reformat Phone Number	C++ Python	O(n)	O(1)	Easy		Inplace
1698	Number of Distinct Substrings in a String	C++ Python	O(n^2)	O(t)	Medium	🔒	Trie
1704	Determine if String Halves Are Alike	C++ Python	O(n)	O(1)	Easy
1763	Longest Nice Substring	C++ Python	O(n)	O(n)	Easy
1768	Merge Strings Alternately	C++ Python	O(m + n)	O(1)	Easy
1784	Check if Binary String Has at Most One Segment of Ones	C++ Python	O(n)	O(1)	Easy
1790	Check if One String Swap Can Make Strings Equal	C++ Python	O(n)	O(1)	Easy
1796	Second Largest Digit in a String	C++ Python	O(n)	O(1)	Easy
1805	Number of Different Integers in a String	C++ Python	O(n)	O(n)	Easy
1813	Sentence Similarity III	C++ Python	O(n)	O(1)	Medium
1816	Truncate Sentence	C++ Python	O(n)	O(1)	Easy
1832	Check if the Sentence Is Pangram	C++ Python	O(n)	O(1)	Easy
1839	Longest Substring Of All Vowels in Order	C++ Python	O(n)	O(1)	Medium
1844	Replace All Digits with Characters	C++ Python	O(n)	O(1)	Easy
1854	Maximum Population Year	C++ Python	O(n)	O(1)	Easy		Line Sweep
1858	Longest Word With All Prefixes	C++ Python	O(n)	O(t)	Medium	🔒	Trie, DFS
1876	Substrings of Size Three with Distinct Characters	C++ Python	O(n)	O(1)	Easy
1880	Check if Word Equals Summation of Two Words	C++ Python	O(n)	O(1)	Easy
1903	Largest Odd Number in String	C++ Python	O(n)	O(1)	Easy
1910	Remove All Occurrences of a Substring	C++ Python	O(n + m)	O(n + m)	Medium		`KMP Algorithm`
1933	Check if String Is Decomposable Into Value-Equal Substrings	C++ Python	O(n)	O(1)	Easy	🔒
1935	Maximum Number of Words You Can Type	C++ Python	O(n)	O(1)	Easy
1957	Delete Characters to Make Fancy String	C++ Python	O(n)	O(1)	Easy		Inplace
1961	Check If String Is a Prefix of Array	C++ Python	O(n)	O(1)	Easy
1963	Minimum Number of Swaps to Make the String Balanced	C++ Python	O(n)	O(1)	Medium	variant of Maximum Nesting Depth of the Parentheses
1967	Number of Strings That Appear as Substrings in Word	C++ Python	O(n l + m)*	O(t)	Easy		`KMP Algorithm`, `Aho-Corasick Automata`, Trie
1974	Minimum Time to Type Word Using Special Typewriter	C++ Python	O(n)	O(1)	Easy
2000	Reverse Prefix of Word	C++ Python	O(n)	O(1)	Easy
2042	Check if Numbers Are Ascending in a Sentence	C++ Python	O(n)	O(1)	Easy
2047	Number of Valid Words in a Sentence	C++ Python	O(n)	O(1)	Easy
2048	Next Greater Numerically Balanced Number	C++ Python	O(1)	O(1)	Medium		Permutations, Precompute, Binary Search
2081	Sum of k-Mirror Numbers	C++ Python	O(10^6)	O(1)	Hard		String, Palindrome, Brute Force
2103	Rings and Rods	C++ Python	O(n)	O(1)	Easy
2108	Find First Palindromic String in the Array	C++ Python	O(n)	O(1)	Easy
2109	Adding Spaces to a String	C++ Python	O(n)	O(1)	Medium		Inplace
2114	Maximum Number of Words Found in Sentences	C++ Python	O(n)	O(1)	Easy
2116	Check if a Parentheses String Can Be Valid	C++ Python	O(n)	O(1)	Medium
2124	Check if All A's Appears Before All B's	C++ Python	O(n)	O(1)	Easy
2129	Capitalize the Title	C++ Python	O(n)	O(1)	Easy
2131	Longest Palindrome by Concatenating Two Letter Words	C++ Python	O(n)	O(n)	Medium
2135	Count Words Obtained After Adding a Letter	C++ Python	O(n)	O(n)	Medium		Bitmasks
2138	Divide a String Into Groups of Size k	C++ Python	O(n)	O(1)	Easy
2156	Find Substring With Given Hash Value	C++ Python	O(n)	O(1)	Medium		`Rabin-Karp Algorithm`, Rolling Hash
2157	Groups of Strings	C++ Python	O(26 n)*	O(26 n)*	Hard		Bitmasks, Union Find
2168	Unique Substrings With Equal Digit Frequency	C++ Python	O(n^2)	O(n^2)	Medium	🔒	`Rabin-Karp Algorithm`, Rolling Hash
2185	Counting Words With a Given Prefix	C++ Python	O(n p)*	O(1)	Easy
2186	Minimum Number of Steps to Make Two Strings Anagram II	C++ Python	O(n)	O(1)	Medium	variant of Minimum Number of Steps to Make Two Strings Anagram
2211	Count Collisions on a Road	C++ Python	O(n)	O(1)	Medium		Counting, Simulation
2213	Longest Substring of One Repeating Character	C++ Python	O(nlogn)	O(n)	Hard		Segment Tree
2223	Sum of Scores of Built Strings	C++ Python	O(n)	O(n)	Hard		`Z-Function`
2232	Minimize Result by Adding Parentheses to Expression	C++ Python	O(n^2)	O(1)	Medium		Brute Force
2243	Calculate Digit Sum of a String	C++ Python	O(n)	O(n)	Easy		Simulation
2255	Count Prefixes of a Given String	C++ Python	O(n l)*	O(1)	Easy		String
2264	Largest 3-Same-Digit Number in String	C++ Python	O(n)	O(1)	Easy		String
2269	Find the K-Beauty of a Number	C++ Python	O(logn)	O(logn)	Easy		Sliding Window
2272	Substring With Largest Variance	C++ Python	O(a^2 n)*	O(a)	Hard		`Kadane's Algorithm`
2273	Find Resultant Array After Removing Anagrams	C++ Python	O(n l)*	O(1)	Easy		Freq Table, Sort

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Linked List

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1171	Remove Zero Sum Consecutive Nodes from Linked List	C++ Python	O(n)	O(n)	Medium		OrderedDict, Hash
1180	Count Substrings with Only One Distinct Letter	C++ Python	O(n)	O(1)	Easy	🔒
1181	Before and After Puzzle	C++ Python	O(l rlogr)*	O(l (n + r))*	Medium	🔒	Hash
1265	Print Immutable Linked List in Reverse	C++ Python	O(n)	O(sqrt(n))	Medium	🔒
1290	Convert Binary Number in a Linked List to Integer	C++ Python	O(n)	O(1)	Easy
1474	Delete N Nodes After M Nodes of a Linked List	C++ Python	O(n)	O(1)	Easy	🔒
1634	Add Two Polynomials Represented as Linked Lists	C++ Python	O(m + n)	O(1)	Medium	🔒
1650	Lowest Common Ancestor of a Binary Tree III	C++ Python	O(h)	O(1)	Medium	🔒, variant of Intersection of Two Linked Lists
1669	Merge In Between Linked Lists	C++ Python	O(m + n)	O(1)	Medium
1721	Swapping Nodes in a Linked List	C++ Python	O(n)	O(1)	Medium
1836	Remove Duplicates From an Unsorted Linked List	C++ Python	O(n)	O(n)	Medium	🔒
2058	Find the Minimum and Maximum Number of Nodes Between Critical Points	C++ Python	O(n)	O(1)	Medium
2074	Reverse Nodes in Even Length Groups	C++ Python	O(n)	O(1)	Medium
2095	Delete the Middle Node of a Linked List	C++ Python	O(n)	O(1)	Medium		Two Pointers
2130	Maximum Twin Sum of a Linked List	C++ Python	O(n)	O(1)	Medium		Two Pointers
2181	Merge Nodes in Between Zeros	C++ Python	O(n)	O(1)	Medium		Two Pointers

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Stack

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1003	Check If Word Is Valid After Substitutions	C++ Python	O(n)	O(n)	Medium
1019	Next Greater Node In Linked List	C++ Python	O(n)	O(n)	Medium		Mono Stack
1021	Remove Outermost Parentheses	C++ Python	O(n)	O(1)	Easy
1047	Remove All Adjacent Duplicates In String	C++ Python	O(n)	O(n)	Easy
1063	Number of Valid Subarrays	C++ Python	O(n)	O(n)	Hard	🔒	Mono Stack
1130	Minimum Cost Tree From Leaf Values	C++ Python	O(n)	O(n)	Medium		Mono Stack
1190	Reverse Substrings Between Each Pair of Parentheses	C++ Python	O(n)	O(n)	Medium
1209	Remove All Adjacent Duplicates in String II	C++ Python	O(n)	O(n)	Medium
1441	Build an Array With Stack Operations	C++ Python	O(n)	O(1)	Easy
1541	Minimum Insertions to Balance a Parentheses String	C++ Python	O(n)	O(1)	Medium
1597	Build Binary Expression Tree From Infix Expression	C++ Python	O(n)	O(n)	Medium	🔒, variant of Basic Calculator III
1856	Maximum Subarray Min-Product	C++ Python	O(n)	O(n)	Medium	variant of Largest Rectangle in Histogram	Mono Stack, Prefix Sum
1944	Number of Visible People in a Queue	C++ Python	O(n)	O(n)	Hard	variant of Buildings With an Ocean View	Mono Stack
1950	Maximum of Minimum Values in All Subarrays	C++ Python	O(n)	O(n)	Medium	🔒	Mono Stack
2104	Sum of Subarray Ranges	C++ Python	O(n)	O(n)	Medium		Mono Stack
2197	Replace Non-Coprime Numbers in Array	C++ Python	O(nlogm)	O(1)	Hard		Stack, Math

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Queue

#	Title	Solution	Time	Space	Difficulty	Note
1424	Diagonal Traverse II	C++ Python	O(m n)*	O(m)	Medium
1438	Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit	C++ Python	O(n)	O(n)	Hard	Mono Deque
1499	Max Value of Equation	C++ Python	O(n)	O(n)	Hard	Mono Deque
1696	Jump Game VI	C++ Python	O(n)	O(k)	Medium	Mono Deque, Sliding Window

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Binary Heap

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1046	Last Stone Weight	C++ Python	O(nlogn)	O(n)	Easy
1057	Campus Bikes	C++ Python	O((w b) * log(w * b))*	O(w b)*	Medium	🔒
1383	Maximum Performance of a Team	C++ Python	O(nlogn)	O(n)	Hard	variant of Minimum Cost to Hire K Workers	Sort
1439	Find the Kth Smallest Sum of a Matrix With Sorted Rows	C++ Python	O(m klogk)*	O(k)	Hard		Binary Search
1606	Find Servers That Handled Most Number of Requests	C++ Python	O(nlogk)	O(k)	Hard		Sorted List
1642	Furthest Building You Can Reach	C++ Python	O(nlogk)	O(k)	Medium
1675	Minimize Deviation in Array	C++ Python	O((n log(max_num)) * logn)*	O(n)	Hard
1792	Maximum Average Pass Ratio	C++ Python	O(n + mlogn)	O(n)	Medium
1882	Process Tasks Using Servers	C++ Python	O(n + mlogn)	O(n)	Medium
1962	Remove Stones to Minimize the Total	C++ Python	O(klogn)	O(1)	Medium
2054	Two Best Non-Overlapping Events	C++ Python	O(nlogn)	O(n)	Medium		Line Sweep, Heap
2163	Minimum Difference in Sums After Removal of Elements	C++ Python	O(nlogn)	O(n)	Hard		Heap, Prefix Sum
2208	Minimum Operations to Halve Array Sum	C++ Python	O(nlogn)	O(n)	Medium		Heap

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Tree

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1008	Construct Binary Search Tree from Preorder Traversal	C++ Python	O(n)	O(h)	Medium
1022	Sum of Root To Leaf Binary Numbers	C++ Python	O(n)	O(h)	Easy
1026	Maximum Difference Between Node and Ancestor	C++ Python	O(n)	O(h)	Medium		DFS
1028	Recover a Tree From Preorder Traversal	C++ Python	O(n)	O(h)	Hard		DFS
1032	Stream of Characters	C++ C++ Python Python	ctor: O(n) query: O(m)	O(t)	Hard		`Aho-Corasick Automata`, Trie
1038	Binary Search Tree to Greater Sum Tree	C++ Python	O(n)	O(h)	Medium		DFS
1065	Index Pairs of a String	C++ Python	O(n + m + z)	O(t)	Easy	🔒	`Aho-Corasick Automata`, Trie
1080	Insufficient Nodes in Root to Leaf Paths	C++ Python	O(n)	O(h)	Medium		DFS
1104	Path In Zigzag Labelled Binary Tree	C++ Python	O(logn)	O(logn)	Easy		Math
1120	Maximum Average Subtree	C++ Python	O(n)	O(h)	Easy	🔒	DFS
1123	Lowest Common Ancestor of Deepest Leaves	C++ Python	O(n)	O(h)	Medium		DFS
1145	Binary Tree Coloring Game	C++ Python	O(n)	O(h)	Medium		DFS
1257	Smallest Common Region	C++ Python	O(m n)*	O(n)	Medium
1261	Find Elements in a Contaminated Binary Tree	C++ Python	O(n)	O(h)	Medium		DFS
1325	Delete Leaves With a Given Value	C++ Python	O(n)	O(h)	Medium		DFS
1339	Maximum Product of Splitted Binary Tree	C++ Python	O(n)	O(h)	Medium		DFS
1409	Queries on a Permutation With Key	C++ Python	O(nlogn)	O(n)	Medium		BIT, Fenwick Tree
1430	Check If a String Is a Valid Sequence from Root to Leaves Path in a Binary Tree	C++ Python	O(n)	O(h)	Medium	🔒	BFS, DFS, Stack
1443	Minimum Time to Collect All Apples in a Tree	C++ Python	O(n)	O(n)	Medium		DFS, Stack
1448	Count Good Nodes in Binary Tree	C++ Python	O(n)	O(h)	Medium		DFS, Stack
1457	Pseudo-Palindromic Paths in a Binary Tree	C++ Python	O(n)	O(h)	Medium		DFS, Stack
1469	Find All The Lonely Nodes	C++ Python	O(n)	O(h)	Easy	🔒	DFS, Stack
1490	Clone N-ary Tree	C++ Python	O(n)	O(h)	Medium	🔒	DFS, Stack
1505	Minimum Possible Integer After at Most K Adjacent Swaps On Digits	C++ Python	O(nlogn)	O(n)	Hard		BIT, Fenwick Tree
1506	Find Root of N-Ary Tree	C++ Python	O(n)	O(1)	Medium	🔒	Bit Manipulation
1516	Move Sub-Tree of N-Ary Tree	C++ Python	O(n)	O(h)	Hard	🔒	DFS, Stack
1519	Number of Nodes in the Sub-Tree With the Same Label	C++ Python	O(n)	O(h)	Medium		DFS, Stack
1522	Diameter of N-Ary Tree	C++ Python	O(n)	O(h)	Medium	🔒	DFS, Stack
1530	Number of Good Leaf Nodes Pairs	C++ Python	O(n)	O(h)	Medium		DFS, Stack
1612	Check If Two Expression Trees are Equivalent	C++ Python	O(n)	O(1)	Medium	🔒	`Morris Traversal`, Inorder Traversal, Stack, Hash Table
1649	Create Sorted Array through Instructions	C++ Python	O(nlogn)	O(n)	Hard	variant of Count of Smaller Numbers After Self	BIT, Fenwick Tree, Merge Sort
1666	Change the Root of a Binary Tree	C++ Python	O(h)	O(1)	Medium	🔒
1834	Single-Threaded CPU	C++ Python	O(nlogn)	O(n)	Medium
1938	Maximum Genetic Difference Query	C++ Python	O(nlogk + mlogk)	O(n + logk)	Hard	variant of Maximum XOR With an Element From Array	DFS, Greedy, Trie
1948	Delete Duplicate Folders in System	C++ Python	O(n m * l + tlogt + l * t)*	O(l t)*	Hard	variant of Find Duplicate Subtrees	Trie, DFS, Hash
2003	Smallest Missing Genetic Value in Each Subtree	C++ Python	O(n)	O(n)	Hard		DFS, Stack
2096	Step-By-Step Directions From a Binary Tree Node to Another	C++ Python	O(n)	O(h)	Medium		DFS, Stack
2179	Count Good Triplets in an Array	C++ Python	O(nlogn)	O(n)	Hard	variant of Create Sorted Array through Instructions	BIT, Fenwick Tree
2196	Create Binary Tree From Descriptions	C++ Python	O(n)	O(n)	Medium
2236	Root Equals Sum of Children	C++ Python	O(1)	O(1)	Easy		Tree

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Hash Table

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1001	Grid Illumination	C++ Python	O(l + q)	O(l)	Hard
1124	Longest Well-Performing Interval	C++ Python	O(n)	O(n)	Medium
1133	Largest Unique Number	C++ Python	O(n)	O(n)	Easy	🔒	Hash
1152	Analyze User Website Visit Pattern	C++ Python	O(n^3)	O(n^3)	Medium	🔒	Hash
1153	String Transforms Into Another String	C++ Python	O(n)	O(1)	Hard	🔒	Hash
1160	Find Words That Can Be Formed by Characters	C++ Python	O(m n)*	O(1)	Easy
1165	Single-Row Keyboard	C++ Python	O(n)	O(1)	Easy	🔒
1198	Find Smallest Common Element in All Rows	C++ Python	O(m n)*	O(n)	Medium	🔒
1207	Unique Number of Occurrences	C++ Python	O(n)	O(n)	Easy
1224	Maximum Equal Frequency	C++ Python	O(n)	O(n)	Hard
1418	Display Table of Food Orders in a Restaurant	C++ Python	O(n + tlogt + flogf)	O(n)	Medium
1452	People Whose List of Favorite Companies Is Not a Subset of Another List	C++ Python	O(n m * l + n^2 * m)*	O(n m * l)*	Medium
1487	Making File Names Unique	C++ Python	O(n)	O(n)	Medium
1577	Number of Ways Where Square of Number Is Equal to Product of Two Numbers	C++ Python	O(m n)*	O(m + n)	Medium
1590	Make Sum Divisible by P	C++ Python	O(n)	O(p)	Medium	variant of Subarray Sums Divisible by K
1640	Check Array Formation Through Concatenation	C++ Python	O(n)	O(n)	Easy
1657	Determine if Two Strings Are Close	C++ Python	O(n)	O(1)	Medium
1679	Max Number of K-Sum Pairs	C++ Python	O(n)	O(n)	Medium
1711	Count Good Meals	C++ Python	O(n)	O(1)	Medium
1748	Sum of Unique Elements	C++ Python	O(n)	O(n)	Easy
1781	Sum of Beauty of All Substrings	C++ Python	O(n^2)	O(1)	Medium
1807	Evaluate the Bracket Pairs of a String	C++ Python	O(n + m)	O(n + m)	Medium
1814	Count Nice Pairs in an Array	C++ Python	O(nlogm)	O(n)	Medium
1817	Finding the Users Active Minutes	C++ Python	O(n)	O(n)	Medium
1915	Number of Wonderful Substrings	C++ Python	O(n)	O(1)	Medium
1923	Longest Common Subpath	C++ Python	O(m nlogn)*	O(n)	Hard		Binary Search, `Rabin-Karp Algorithm`
1925	Count Square Sum Triples	C++ Python	O(n^2)	O(n)	Easy
1930	Unique Length-3 Palindromic Subsequences	C++ Python	O(n)	O(1)	Medium
1941	Check if All Characters Have Equal Number of Occurrences	C++ Python	O(n)	O(1)	Easy
1995	Count Special Quadruplets	C++ Python	O(n^3)	O(n)	Easy	variant of 4 Sum
2006	Count Number of Pairs With Absolute Difference K	C++ Python	O(n)	O(n)	Easy	variant of Two Sum
2023	Number of Pairs of Strings With Concatenation Equal to Target	C++ Python	O(n l)*	O(n)	Medium	variant of Two Sum
2025	Maximum Number of Ways to Partition an Array	C++ Python	O(n)	O(n)	Hard		Prefix Sum
2032	Two Out of Three	C++ Python	O(n)	O(min(n, r))	Easy		Counting
2053	Kth Distinct String in an Array	C++ Python	O(n)	O(n)	Easy
2068	Check Whether Two Strings are Almost Equivalent	C++ Python	O(n)	O(1)	Easy
2085	Count Common Words With One Occurrence	C++ Python	O(m + n)	O(m + n)	Easy
2120	Execution of All Suffix Instructions Staying in a Grid	C++ Python	O(m)	O(m)	Medium
2150	Find All Lonely Numbers in the Array	C++ Python	O(n)	O(n)	Medium
2154	Keep Multiplying Found Values by Two	C++ Python	O(n)	O(n)	Easy
2170	Minimum Operations to Make the Array Alternating	C++ Python	O(n)	O(n)	Medium		Freq Table
2190	Most Frequent Number Following Key In an Array	C++ Python	O(n)	O(n)	Easy		Freq Table
2201	Count Artifacts That Can Be Extracted	C++ Python	O(a + d)	O(d)	Medium		Hash Table
2206	Divide Array Into Equal Pairs	C++ Python	O(n)	O(n)	Easy		Hash Table
2215	Find the Difference of Two Arrays	C++ Python	O(n)	O(n)	Easy		Hash Table
2225	Find Players With Zero or One Losses	C++ Python	O(nlogn)	O(n)	Medium		Hash Table, Sort
2229	Check if an Array Is Consecutive	C++ Python	O(n)	O(n)	Easy	🔒	Hash Table, Sort
2260	Minimum Consecutive Cards to Pick Up	C++ Python	O(n)	O(n)	Medium		Hash Table
2261	K Divisible Elements Subarrays	C++ Python	O(n^2)	O(t)	Medium		Trie, `Rabin-Karp Algorithm`

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Math

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1006	Clumsy Factorial	C++ Python	O(1)	O(1)	Medium
1009	Complement of Base 10 Integer	C++ Python	O(logn)	O(1)	Easy
1012	Numbers With Repeated Digits	C++ Python	O(logn)	O(logn)	Hard
1015	Smallest Integer Divisible by K	C++ Python	O(k)	O(1)	Medium
1017	Convert to Base -2	C++ Python	O(logn)	O(1)	Medium
1025	Divisor Game	C++ Python	O(1)	O(1)	Easy		DP
1037	Valid Boomerang	C++ Python	O(1)	O(1)	Easy
1041	Robot Bounded In Circle	C++ Python	O(n)	O(1)	Medium
1067	Digit Count in Range	C++ Python	O(logn)	O(1)	Hard	🔒, variant of Number of Digit One
1073	Adding Two Negabinary Numbers	C++ Python	O(n)	O(n)	Medium
1079	Letter Tile Possibilities	C++ Python	O(n^2)	O(n)	Medium		Generating Function, Backtracking
1088	Confusing Number II	C++ Python	O(logn)	O(logn)	Hard	🔒
1103	Distribute Candies to People	C++ Python	O(n + logc)	O(1)	Easy		Binary Search
1118	Number of Days in a Month	C++ Python	O(1)	O(1)	Easy	🔒
1121	Divide Array Into Increasing Sequences	C++ Python	O(n)	O(1)	Hard	🔒
1128	Number of Equivalent Domino Pairs	C++ Python	O(n)	O(n)	Easy
1131	Maximum of Absolute Value Expression	C++ Python	O(n)	O(1)	Medium
1134	Armstrong Number	C++ Python	O(klogk)	O(k)	Easy	🔒
1150	Check If a Number Is Majority Element in a Sorted Array	C++ Python	O(nlogn)	O(1)	Easy	🔒	Binary Search
1157	Online Majority Element In Subarray	C++ Python	ctor: O(n) query: O(klogn)	O(n)	Hard		Binary Search, Segment Tree, `Boyer–Moore Majority Vote Algorithm`
1154	Day of the Year	C++ Python	O(1)	O(1)	Easy
1175	Prime Arrangements	C++ Python	O(nlog(logn))	O(n)	Easy		`Sieve of Eratosthenes`
1185	Day of the Week	C++ Python	O(1)	O(1)	Easy		`Zeller Formula`
1197	Minimum Knight Moves	C++ Python	O(1)	O(1)	Medium	🔒	DP, Math
1217	Play with Chips	C++ Python	O(n)	O(1)	Medium
1227	Airplane Seat Assignment Probability	C++ Python	O(1)	O(1)	Medium
1232	Check If It Is a Straight Line	C++ Python	O(1)	O(1)	Easy
1237	Find Positive Integer Solution for a Given Equation	C++ Python	O(n)	O(1)	Easy
1238	Circular Permutation in Binary Representation	C++ Python	O(2^n)	O(1)	Medium	variant of Gray Code
1250	Check If It Is a Good Array	C++ Python	O(n)	O(1)	Hard		`Bézout's identity`
1256	Encode Number	C++ Python	O(logn)	O(1)	Medium
1259	Handshakes That Don't Cross	C++ Python	O(n)	O(1)	Hard		`Catalan Number`, DP
1266	Minimum Time Visiting All Points	C++ Python	O(n)	O(1)	Easy
1276	Number of Burgers with No Waste of Ingredients	C++ Python	O(1)	O(1)	Medium
1281	Subtract the Product and Sum of Digits of an Integer	C++ Python	O(logn)	O(1)	Easy
1300	Sum of Mutated Array Closest to Target	C++ Python	O(nlogn)	O(1)	Medium		Binary Search
1317	Convert Integer to the Sum of Two No-Zero Integers	C++ Python	O(logn)	O(1)	Easy
1323	Maximum 69 Number	C++ Python	O(logn)	O(1)	Easy
1330	Reverse Subarray To Maximize Array Value	C++ Python	O(n)	O(1)	Hard
1344	Angle Between Hands of a Clock	C++ Python	O(1)	O(1)	Medium
1359	Count All Valid Pickup and Delivery Options	C++ Python	O(n)	O(1)	Hard
1360	Number of Days Between Two Dates	C++ Python	O(1)	O(1)	Easy	variant of Day of the Year
1362	Closest Divisors	C++ Python	O(sqrt(n))	O(1)	Medium
1363	Largest Multiple of Three	C++ Python	O(n)	O(1)	Hard
1390	Four Divisors	C++ Python	O(n sqrt(n))*	O(1)	Medium
1401	Circle and Rectangle Overlapping	C++ Python	O(1)	O(1)	Medium
1415	The k-th Lexicographical String of All Happy Strings of Length n	C++ Python	O(n)	O(1)	Medium
1442	Count Triplets That Can Form Two Arrays of Equal XOR	C++ Python	O(n)	O(n)	Medium
1447	Simplified Fractions	C++ Python	O(n^2 logn)*	O(n^2)	Medium
1486	XOR Operation in an Array	C++ Python	O(1)	O(1)	Easy
1492	The kth Factor of n	C++ Python	O(sqrt(n))	O(1)	Medium
1497	Check If Array Pairs Are Divisible by k	C++ Python	O(n)	O(k)	Medium
1512	Number of Good Pairs	C++ Python	O(n)	O(1)	Easy
1513	Number of Substrings With Only 1s	C++ Python	O(n)	O(1)	Medium
1525	Number of Good Ways to Split a String	C++ Python	O(n)	O(1)	Medium
1537	Get the Maximum Score	C++ Python	O(m + n)	O(1)	Hard
1551	Minimum Operations to Make Array Equal	C++ Python	O(1)	O(1)	Medium
1611	Minimum One Bit Operations to Make Integers Zero	C++ Python	O(logn)	O(1)	Hard	variant of Gray Code
1641	Count Sorted Vowel Strings	C++ Python	O(1)	O(1)	Medium		Binomial Coefficients
1643	Kth Smallest Instructions	C++ Python	O((m + n)^2)	O(1)	Hard		Binomial Coefficients
1735	Count Ways to Make Array With Product	C++ Python	O(nlogn)	O(logn)	Hard		Binomial Coefficients, `Euler's Theorem`, Modular Inverse
1739	Building Boxes	C++ Python	O(1)	O(1)	Hard
1744	Can You Eat Your Favorite Candy on Your Favorite Day?	C++ Python	O(n)	O(n)	Medium		Prefix Sum
1753	Maximum Score From Removing Stones	C++ Python	O(1)	O(1)	Medium
1776	Car Fleet II	C++ Python	O(n)	O(n)	Hard		Mono Stack
1780	Check if Number is a Sum of Powers of Three	C++ Python	O(logn)	O(1)	Medium
1806	Minimum Number of Operations to Reinitialize a Permutation	C++ Python	O(sqrt(n))	O(sqrt(n))	Medium		Discrete Logarithm, Multiplicative Order
1808	Maximize Number of Nice Divisors	C++ Python	O(logn)	O(1)	Medium	variant of Integer Break
1812	Determine Color of a Chessboard Square	C++ Python	O(1)	O(1)	Easy
1819	Number of Different Subsequences GCDs	C++ Python	O(n + mlogm)	O(n)	Hard
1822	Sign of the Product of an Array	C++ Python	O(n)	O(1)	Easy
1823	Find the Winner of the Circular Game	C++ Python	O(n)	O(1)	Medium
1828	Queries on Number of Points Inside a Circle	C++ Python	O(q n)*	O(1)	Medium
1830	Minimum Number of Operations to Make String Sorted	C++ Python	O(n)	O(max_n)	Hard		Modular Inverse
1835	Find XOR Sum of All Pairs Bitwise AND	C++ Python	O(n)	O(1)	Hard
1837	Sum of Digits in Base K	C++ Python	O(logn)	O(1)	Easy
1860	Incremental Memory Leak	C++ Python	O(1)	O(1)	Medium	GCJ2020 - Round 2
1862	Sum of Floored Pairs	C++ Python	O(nlogn)	O(n)	Hard
1863	Sum of All Subset XOR Totals	C++ Python	O(n)	O(1)	Easy
1884	Egg Drop With 2 Eggs and N Floors	C++ Python	O(1)	O(1)	Medium		DP
1904	The Number of Full Rounds You Have Played	C++ Python	O(1)	O(1)	Medium
1916	Count Ways to Build Rooms in an Ant Colony	C++ Python	O(n)	O(n)	Hard		DFS, Tree
1922	Count Good Numbers	C++ Python	O(logn)	O(1)	Medium
1945	Sum of Digits of String After Convert	C++ Python	O(n)	O(1)	Easy
1952	Three Divisors	C++ Python	O(sqrt(n))	O(1)	Easy
1954	Minimum Garden Perimeter to Collect Enough Apples	C++ Python	O(1)	O(1)	Medium		Binary Search, `Cardano's Formula`
1969	Minimum Non-Zero Product of the Array Elements	C++ Python	O(min(p, logM))	O(1)	Medium
1979	Find Greatest Common Divisor of Array	C++ Python	O(n)	O(1)	Easy
1980	Find Unique Binary String	C++ Python	O(n)	O(1)	Medium		`Cantor Diagonalization`
1982	Find Array Given Subset Sums	C++ Python	O(n 2^n)*	O(1)	Hard		Math, DP, OrderedDict
2001	Number of Pairs of Interchangeable Rectangles	C++ Python	O(n)	O(n)	Medium		Math
2005	Subtree Removal Game with Fibonacci Tree	C++ Python	O(1)	O(1)	Hard	🔒	Math, `Sprague-Grundy Theorem`, `Colon Principle`
2028	Find Missing Observations	C++ Python	O(n)	O(1)	Medium
2029	Stone Game IX	C++ Python	O(n)	O(1)	Medium
2063	Vowels of All Substrings	C++ Python	O(n)	O(1)	Medium		Combinatorics
2073	Time Needed to Buy Tickets	C++ Python	O(n)	O(1)	Easy		Simulation, Math
2083	Substrings That Begin and End With the Same Letter	C++ Python	O(n)	O(1)	Medium	🔒	Combinatorics
2091	Removing Minimum and Maximum From Array	C++ Python	O(n)	O(1)	Medium		Math
2110	Number of Smooth Descent Periods of a Stock	C++ Python	O(n)	O(1)	Medium		Math, Combinatorics
2117	Abbreviating the Product of a Range	C++ Python	O(r - l)	O(1)	Hard		Math
2119	A Number After a Double Reversal	C++ Python	O(1)	O(1)	Easy		Math
2125	Number of Laser Beams in a Bank	C++ Python	O(m n)*	O(1)	Medium		Math
2133	Check if Every Row and Column Contains All Numbers	C++ Python	O(n^2)	O(n)	Easy		Math
2145	Count the Hidden Sequences	C++ Python	O(n)	O(1)	Medium		Math
2148	Count Elements With Strictly Smaller and Greater Elements	C++ Python	O(n)	O(1)	Easy		Math
2152	Minimum Number of Lines to Cover Points	C++ Python	O(n 2^n)*	O(n^2)	Medium	🔒	Math, Hash Table, Bitmasks
2169	Count Operations to Obtain Zero	C++ Python	O(log(min(m, n)))	O(1)	Easy		Math, `Euclidean Algorithm`
2171	Removing Minimum Number of Magic Beans	C++ Python	O(nlogn)	O(1)	Medium		Math, Sort
2176	Count Equal and Divisible Pairs in an Array	C++ Python	O(nlogk + n sqrt(k))*	O(n + sqrt(k))	Easy		Math
2177	Find Three Consecutive Integers That Sum to a Given Number	C++ Python	O(1)	O(1)	Medium		Math
2180	Count Integers With Even Digit Sum	C++ Python	O(logn)	O(1)	Easy		Math
2183	Count Array Pairs Divisible by K	C++ Python	O(nlogk + k)	O(sqrt(k))	Hard	variant of Count Equal and Divisible Pairs in an Array	Math
2198	Number of Single Divisor Triplets	C++ Python	O(d^3)	O(d)	Medium	🔒	Math, Combinatorics
2217	Find Palindrome With Fixed Length	C++ Python	O(n l)*	O(1)	Medium		Math
2221	Find Triangular Sum of an Array	C++ Python	O(n)	O(1)	Medium		Simulation, Combinatorics, Number Thoery
2235	Add Two Integers	C++ Python	O(1)	O(1)	Easy		Math
2240	Number of Ways to Buy Pens and Pencils	C++ Python	O(sqrt(t))	O(1)	Medium		Math
2244	Minimum Rounds to Complete All Tasks	C++ Python	O(n)	O(n)	Medium		Math, Freq Table
2249	Count Lattice Points Inside a Circle	C++ Python	O(n r^2)*	O(min(n r^2, max_x * max_y))*	Medium		Math, Hash Table
2262	Total Appeal of A String	C++ Python	O(n)	O(26)	Hard	variant of Count Unique Characters of All Substrings of a Given String	Combinatorics

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Sort

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1054	Distant Barcodes	C++ Python	O(klogk)	O(k)	Medium	variant of Rearrange String k Distance Apart
1086	High Five	C++ Python	O(nlogn)	O(n)	Easy	🔒
1094	Car Pooling	C++ Python	O(nlogn)	O(n)	Medium	variant of Meeting Rooms II
1122	Relative Sort Array	C++ Python	O(nlogn)	O(n)	Easy
1229	Meeting Scheduler	C++ Python	O(nlogn)	O(n)	Medium		Line Sweep, Heap
1356	Sort Integers by The Number of 1 Bits	C++ Python	O(nlogn)	O(1)	Easy		Bit Manipulation
1365	How Many Numbers Are Smaller Than the Current Number	C++ Python	O(n + m)	O(m)	Easy		Counting Sort
1366	Rank Teams by Votes	C++ Python	O(m (n + mlogm))*	O(m^2)	Medium
1451	Rearrange Words in a Sentence	C++ Python	O(nlogn)	O(n)	Medium		String
1481	Least Number of Unique Integers after K Removals	C++ Python	O(n)	O(n)	Medium		Counting Sort
1509	Minimum Difference Between Largest and Smallest Value in Three Moves	C++ Python	O(n + klogk)	O(1)	Medium		Quick Select
1523	Count Odd Numbers in an Interval Range	C++ Python	O(1)	O(1)	Easy
1561	Maximum Number of Coins You Can Get	C++ Python	O(nlogn)	O(1)	Medium
1588	Sum of All Odd Length Subarrays	C++ Python	O(n)	O(1)	Easy
1608	Special Array With X Elements Greater Than or Equal X	C++ Python	O(n)	O(1)	Easy	variant of H-Index	Counting Sort, Binary Search
1620	Coordinate With Maximum Network Quality	C++ Python	O(n^2)	O(1)	Medium
1621	Number of Sets of K Non-Overlapping Line Segments	C++ Python	O(1)	O(n)	Medium		Binomial Coefficients, `Euler's Theorem`
1630	Arithmetic Subarrays	C++ Python	O(n q)*	O(n)	Medium		Arithmetic Series
1636	Sort Array by Increasing Frequency	C++ Python	O(nlogn)	O(n)	Easy
1637	Widest Vertical Area Between Two Points Containing No Points	C++ Python	O(nlogn)	O(n)	Medium
1680	Concatenation of Consecutive Binary Numbers	C++ Python	O(n)	O(1)	Medium
1685	Sum of Absolute Differences in a Sorted Array	C++ Python	O(n)	O(1)	Medium
1688	Count of Matches in Tournament	C++ Python	O(1)	O(1)	Easy
1703	Minimum Adjacent Swaps for K Consecutive Ones	C++ Python	O(n)	O(n)	Hard		Math, Median, Prefix Sum
1716	Calculate Money in Leetcode Bank	C++ Python	O(1)	O(1)	Easy		Arithmetic Sequence
1772	Sort Features by Popularity	C++ Python	O(n)	O(1)	Medium	🔒
1847	Closest Room	C++ Python	O(nlogn + klogk + klogn)	O(n + k)	Hard		Sort, Binary Search
1851	Minimum Interval to Include Each Query	C++ Python	O(nlogn + klogk + klogn)	O(n + k)	Hard		Sort, Heap, Line Sweep
1859	Sorting the Sentence	C++ Python	O(n)	O(n)	Easy		Sort, String
1942	The Number of the Smallest Unoccupied Chair	C++ Python	O(nlogn)	O(n)	Medium		Line Sweep, Heap
1943	Describe the Painting	C++ Python	O(nlogn)	O(n)	Medium		Line Sweep
1968	Array With Elements Not Equal to Average of Neighbors	C++ Python	O(n) on average	O(1)	Medium	variant of Wiggle Sort II	Quick Select, Tri Partition
1985	Find the Kth Largest Integer in the Array	C++ Python	O(n) on average	O(n)	Medium		Quick Select
1996	The Number of Weak Characters in the Game	C++ Python	O(nlogn)	O(1)	Medium
2015	Average Height of Buildings in Each Segment	C++ Python	O(nlogn)	O(n)	Medium	🔒	Line Sweep
2021	Brightest Position on Street	C++ Python	O(nlogn)	O(n)	Medium	🔒	Line Sweep
2070	Most Beautiful Item for Each Query	C++ Python	O(nlogn + qlogn)	O(1)	Medium		Sort, Binary Search
2089	Find Target Indices After Sorting Array	C++ Python	O(n)	O(1)	Easy		Counting Sort
2158	Amount of New Area Painted Each Day	C++ Python	O(nlogr)	O(r)	Hard	🔒	Line Sweep, Sorted List, Heap, Segment Tree
2164	Sort Even and Odd Indices Independently	C++ Python	O(n)	O(c)	Easy		Counting Sort, Inplace
2191	Sort the Jumbled Numbers	C++ Python	O(nlogm + nlogn)	O(n)	Medium		Sort
2231	Largest Number After Digit Swaps by Parity	C++ Python	O(logn)	O(1)	Easy		Counting Sort
2233	Maximum Product After K Increments	C++ Python	O(n + k)	O(n)	Medium		Heap, Freq Table, Sort, Math
2248	Intersection of Multiple Arrays	C++ Python	O(n l + r)*	O(l)	Easy		Hash Table, Counting Sort
2251	Number of Flowers in Full Bloom	C++ Python	O(nlogn + mlogn)	O(n)	Hard		Line Sweep, Binary Search

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Two Pointers

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1004	Max Consecutive Ones III	C++ Python	O(n)	O(1)	Medium		Sliding Window
1033	Moving Stones Until Consecutive	C++ Python	O(1)	O(1)	Easy
1040	Moving Stones Until Consecutive II	C++ Python	O(nlogn)	O(1)	Medium
1151	Minimum Swaps to Group All 1's Together	C++ Python	O(n)	O(1)	Medium	🔒	Sliding Window
1156	Swap For Longest Repeated Character Substring	C++ Python	O(n)	O(1)	Medium		Sliding Window
1176	Diet Plan Performance	C++ Python	O(n)	O(1)	Easy		Sliding Window
1208	Get Equal Substrings Within Budget	C++ Python	O(n)	O(1)	Medium		Sliding Window
1213	Intersection of Three Sorted Arrays	C++ Python	O(n)	O(1)	Easy	🔒
1169	Invalid Transactions	C++ Python	O(nlogn)	O(n)	Medium		Sliding Window, Line Sweep
1214	Two Sum BSTs	C++ Python	O(n)	O(n)	Medium	🔒	Stack
1234	Replace the Substring for Balanced String	C++ Python	O(n)	O(t)	Medium		Two Pointers, Sliding Window
1248	Count Number of Nice Subarrays	C++ Python	O(n)	O(k)	Medium	variant of Subarrays with K Different Integers	Two Pointers, Sliding Window
1297	Maximum Number of Occurrences of a Substring	C++ Python	O(n)	O(n)	Medium		Sliding Window, `Rabin-Karp Algorithm`
1305	All Elements in Two Binary Search Trees	C++ Python	O(n)	O(h)	Medium		Stack
1316	Distinct Echo Substrings	C++ Python	O(n^2 + d)	O(r)	Hard		`KMP Algorithm`, Sliding Window, `Rabin-Karp Algorithm`
1358	Number of Substrings Containing All Three Characters	C++ Python	O(n)	O(1)	Medium		Sliding Window
1423	Maximum Points You Can Obtain from Cards	C++ Python	O(n)	O(1)	Medium		Sliding Window
1425	Constrained Subset Sum	C++ Python	O(n)	O(k)	Hard	variant of Sliding Window Maximum	Mono Deque, Sliding Window
1456	Maximum Number of Vowels in a Substring of Given Length	C++ Python	O(n)	O(1)	Medium		Sliding Window
1493	Longest Subarray of 1's After Deleting One Element	C++ Python	O(n)	O(1)	Medium		Sliding Window
1498	Number of Subsequences That Satisfy the Given Sum Condition	C++ Python	O(nlogn)	O(n)	Medium		Two Pointers
1508	Range Sum of Sorted Subarray Sums	C++ Python	O(nlog(sum(nums)))	O(n)	Medium		Binary Search, Two Pointers, Sliding Window
1521	Find a Value of a Mysterious Function Closest to Target	C++ Python	O(nlogm)	O(logm)	Hard		DP, Two Pointers, Sliding Window
1604	Alert Using Same Key-Card Three or More Times in a One Hour Period	C++ Python	O(nlogn)	O(n)	Medium		Two Pointers, Sliding Window
1658	Minimum Operations to Reduce X to Zero	C++ Python	O(n)	O(1)	Medium		Two Pointers
1687	Delivering Boxes from Storage to Ports	C++ Python	O(nlogn)	O(n)	Hard		Two Pointers, Sliding Window
1695	Maximum Erasure Value	C++ Python	O(n)	O(n)	Medium		Two Pointers, Sliding Window
1712	Ways to Split Array Into Three Subarrays	C++ Python	O(n)	O(n)	Medium		Two Pointers, Prefix Sum
1750	Minimum Length of String After Deleting Similar Ends	C++ Python	O(n)	O(1)	Medium		Two Pointers
1838	Frequency of the Most Frequent Element	C++ Python	O(nlogn)	O(n)	Medium		Two Pointers, Sliding Window
1852	Distinct Numbers in Each Subarray	C++ Python	O(n)	O(k)	Medium	🔒	Two Pointers, Sliding Window
1855	Maximum Distance Between a Pair of Values	C++ Python	O(n + m)	O(1)	Medium		Two Pointers
1868	Product of Two Run-Length Encoded Arrays	C++ Python	O(m + n)	O(1)	Medium	🔒	Two Pointers
1885	Count Pairs in Two Arrays	C++ Python	O(nlogn)	O(1)	Medium	🔒	Two Pointers
1888	Minimum Number of Flips to Make the Binary String Alternatings	C++ Python	O(n)	O(1)	Medium		Two Pointers, Sliding Window
1984	Minimum Difference Between Highest and Lowest of K Scores	C++ Python	O(nlogn)	O(1)	Easy		Two Pointers, Sliding Window
1989	Maximum Number of People That Can Be Caught in Tag	C++ Python	O(n)	O(1)	Medium	🔒	Greedy, Two Pointers, Sliding Window
2009	Minimum Number of Operations to Make Array Continuous	C++ Python	O(nlogn)	O(1)	Hard		Two Pointers, Sliding Window
2024	Maximize the Confusion of an Exam	C++ Python	O(n)	O(1)	Medium	variant of Longest Repeating Character Replacement	Sliding Window
2040	Kth Smallest Product of Two Sorted Arrays	C++ Python	O((m + n) logr)*	O(1)	Hard		Binary Search, Two Pointers
2046	Sort Linked List Already Sorted Using Absolute Values	C++ Python	O(n)	O(1)	Medium	🔒	Linked List
2062	Count Vowel Substrings of a String	C++ Python	O(n)	O(1)	Easy	variant of Count Number of Nice Subarrays	Sliding Window
2067	Number of Equal Count Substrings	C++ Python	O(n)	O(1)	Medium	🔒	Sliding Window
2090	K Radius Subarray Averages	C++ Python	O(n)	O(1)	Medium		Sliding Window
2105	Watering Plants II	C++ Python	O(n)	O(1)	Medium		Simulation
2107	Number of Unique Flavors After Sharing K Candies	C++ Python	O(n)	O(n)	Medium	🔒	Sliding Window
2134	Minimum Swaps to Group All 1's Together II	C++ Python	O(n)	O(1)	Medium		Sliding Window
2149	Rearrange Array Elements by Sign	C++ Python	O(n)	O(1)	Medium		Two Pointers
2161	Partition Array According to Given Pivot	C++ Python	O(n)	O(n)	Medium		Two Pointers
2200	Find All K-Distant Indices in an Array	C++ Python	O(n)	O(1)	Easy		Two Pointers
2234	Maximum Total Beauty of the Gardens	C++ Python	O(nlogn)	O(1)	Hard		Sort, Prefix Sum, Greedy, Binary Search, Two Pointers

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Recursion

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1106	Parsing A Boolean Expression	C++ Python	O(n)	O(n)	Hard

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Binary Search

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1011	Capacity To Ship Packages Within D Days	C++ Python	O(nlogr)	O(1)	Medium
1044	Longest Duplicate Substring	C++ Python	O(nlogn)	O(n)	Hard		`Rabin-Karp Algorithm`, Suffix Tree, `Ukkonen's Algorithm`
1060	Missing Element in Sorted Array	C++ Python	O(logn)	O(1)	Medium	🔒
1062	Longest Repeating Substring	C++ Python	O(nlogn)	O(n)	Medium	🔒	`Rabin-Karp Algorithm`
1064	Fixed Point	C++ Python	O(logn)	O(1)	Easy	🔒
1095	Find in Mountain Array	C++ Python	O(logn)	O(1)	Hard
1110	Delete Nodes And Return Forest	C++ Python	O(n)	O(h + d)	Medium
1170	Compare Strings by Frequency of the Smallest Character	C++ Python	O((m + n)logn)	O(n)	Easy
1201	Ugly Number III	C++ Python	O(logn)	O(1)	Medium		Inclusion-Exclusion Principle
1228	Missing Number In Arithmetic Progression	C++ Python	O(logn)	O(1)	Easy
1231	Divide Chocolate	C++ Python	O(nlogn)	O(1)	Hard
1274	Number of Ships in a Rectangle	C++ Python	O(log(m n))*	O(log(m n))*	Hard		Divide and Conquer
1283	Find the Smallest Divisor Given a Threshold	C++ Python	O(logn)	O(1)	Medium
1287	Element Appearing More Than 25% In Sorted Array	C++ Python	O(logn)	O(1)	Easy
1385	Find the Distance Value Between Two Arrays	C++ Python	O((n + m) logm)*	O(1)	Easy		Binary Search, Two Pointers
1482	Minimum Number of Days to Make m Bouquets	C++ Python	O(nlogd)	O(1)	Medium
1533	Find the Index of the Large Integer	C++ Python	O(logn)	O(1)	Medium	🔒
1539	Kth Missing Positive Number	C++ Python	O(logn)	O(1)	Easy
1552	Magnetic Force Between Two Balls	C++ Python	O(nlogn + nlogr)	O(1)	Medium
1618	Maximum Font to Fit a Sentence in a Screen	C++ Python	O(n + logm)	O(1)	Medium	🔒
1648	Sell Diminishing-Valued Colored Balls	C++ Python	O(nlogm)	O(1)	Medium
1671	Minimum Number of Removals to Make Mountain Array	C++ Python	O(nlogn)	O(n)	Medium	variant of Longest Increasing Subsequence	Binary Search, DP
1713	Minimum Operations to Make a Subsequence	C++ Python	O(nlogn)	O(n)	Hard	variant of Longest Increasing Subsequence	Binary Search, Segment Tree
1760	Minimum Limit of Balls in a Bag	C++ Python	O(nlogm)	O(1)	Medium
1802	Maximum Value at a Given Index in a Bounded Array	C++ Python	O(logm)	O(1)	Medium
1818	Minimum Absolute Sum Difference	C++ Python	O(nlogn)	O(n)	Medium
1870	Minimum Speed to Arrive on Time	C++ Python	O(nlogr)	O(1)	Medium
1889	Minimum Space Wasted From Packaging	C++ Python	O(mlogm + nlogn + mlogn)	O(1)	Hard
1891	Cutting Ribbons	C++ Python	O(nlogr)	O(1)	Medium	🔒
1898	Maximum Number of Removable Characters	C++ Python	O(rlogn)	O(r)	Medium
1901	Find a Peak Element II	C++ Python	O(min(n, m) log(max(n, m)))*	O(1)	Medium
1918	Kth Smallest Subarray Sum	C++ Python	O(nlogr)	O(1)	Medium	🔒
1964	Find the Longest Valid Obstacle Course at Each Position	C++ Python	O(nlogn)	O(n)	Hard	variant of Longest Increasing Subsequence	Binary Search, Segment Tree, DP
2064	Minimized Maximum of Products Distributed to Any Store	C++ Python	O(nlogm)	O(1)	Medium	variant of Minimum Limit of Balls in a Bag
2111	Minimum Operations to Make the Array K-Increasing	C++ Python	O(nlog(n/k))	O(n/k)	Hard	variant of Longest Increasing Subsequence
2137	Pour Water Between Buckets to Make Water Levels Equal	C++ Python	O(nlogr)	O(1)	Medium	🔒
2187	Minimum Time to Complete Trips	C++ Python	O(nlogr)	O(1)	Medium
2226	Maximum Candies Allocated to K Children	C++ Python	O(nlogr)	O(1)	Medium		Binary Search
2250	Count Number of Rectangles Containing Each Point	C++ Python	O(nlogn + m max_y * logn)*	O(n)	Medium		Bucket Sort, Binary Search

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Binary Search Tree

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1373	Maximum Sum BST in Binary Tree	C++ Python	O(n)	O(h)	Hard		DFS, Stack
1382	Balance a Binary Search Tree	C++ Python	O(n)	O(h)	Medium		DFS, Stack
1902	Depth of BST Given Insertion Order	C++ Python	O(nlogn)	O(n)	Medium	🔒	Sorted Dict
1932	Merge BSTs to Create Single BST	C++ Python	O(n)	O(n)	Hard		BST, BFS

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Breadth-First Search

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1034	Coloring A Border	C++ Python	O(m n)*	O(m + n)	Medium
1036	Escape a Large Maze	C++ Python	O(n^2)	O(n)	Hard
1091	Shortest Path in Binary Matrix	C++ Python	O(n^2)	O(n)	Medium
1102	Path With Maximum Minimum Value	C++ Python	O((m n) * log(m * n))*	O(m n)*	Medium	🔒	Binary Search, DFS, `Dijkstra's Algorithm`
1129	Shortest Path with Alternating Colors	C++ Python	O(n + e)	O(n + e)	Medium
1136	Parallel Courses	C++ Python	O(\|V\| + \|E\|)	O(\|E\|)	Hard	🔒	Topological Sort
1161	Maximum Level Sum of a Binary Tree	C++ Python	O(n)	O(w)	Medium		DFS
1162	As Far from Land as Possible	C++ Python	O(m n)*	O(m n)*	Medium
1203	Sort Items by Groups Respecting Dependencies	C++ Python	O(n + e)	O(n + e)	Hard		Topological Sort
1210	Minimum Moves to Reach Target with Rotations	C++ Python	O(n)	O(n)	Hard
1215	Stepping Numbers	C++ Python	O(logk + r)	O(k)	Medium	🔒	Precompute, Binary Search
1245	Tree Diameter	C++ Python	O(\|V\| + \|E\|)	O(\|E\|)	Medium
1263	Minimum Moves to Move a Box to Their Target Location	C++ Python	O(m^2 n^2)*	O(m^2 n^2)*	Hard		`A* Search Algorithm`
1284	Minimum Number of Flips to Convert Binary Matrix to Zero Matrix	C++ Python	O((m n) * 2^(m * n))*	O((m n) * 2^(m * n))*	Hard
1291	Sequential Digits	C++ Python	O(1)	O(1)	Medium
1293	Shortest Path in a Grid with Obstacles Elimination	C++ Python	O(m n * k)*	O(m n)*	Hard		`A* Search Algorithm`
1298	Maximum Candies You Can Get from Boxes	C++ Python	O(n^2)	O(n)	Hard
1302	Deepest Leaves Sum	C++ Python	O(n)	O(w)	Medium
1306	Jump Game III	C++ Python	O(n)	O(n)	Medium
1311	Get Watched Videos by Your Friends	C++ Python	O(n + vlogv)	O(w)	Medium
1345	Jump Game IV	C++ Python	O(n)	O(n)	Hard
1368	Minimum Cost to Make at Least One Valid Path in a Grid	C++ Python	O(m n)*	O(m n)*	Hard		`A* Search Algorithm`, 0-1 BFS, Deque
1514	Path with Maximum Probability	C++ Python	O(\|E\| log\|V\|)*	O(\|E\|)	Medium		`Dijkstra's Algorithm`
1602	Find Nearest Right Node in Binary Tree	C++ Python	O(n)	O(w)	Medium	🔒
1609	Even Odd Tree	C++ Python	O(n)	O(w)	Medium
1625	Lexicographically Smallest String After Applying Operations	C++ Python	O(n^2)	O(1)	Medium		BFS, String
1654	Minimum Jumps to Reach Home	C++ Python	O(max(x, max(forbidden)) + a + b)	O(max(x, max(forbidden)) + a + b)	Medium		BFS
1660	Correct a Binary Tree	C++ Python	O(n)	O(w)	Medium	🔒	BFS
1728	Cat and Mouse II	C++ Python	O((m n)^2 * (m + n))*	O((m n)^2)*	Hard	variant of Cat and Mouse	MiniMax, Topological Sort
1730	Shortest Path to Get Food	C++ Python	O(m n)*	O(m + n)	Medium	🔒	BFS
1765	Map of Highest Peak	C++ Python	O(m n)*	O(m n)*	Medium		BFS
1926	Nearest Exit from Entrance in Maze	C++ Python	O(m n)*	O(m + n)	Medium		Bi-BFS
1928	Minimum Cost to Reach Destination in Time	C++ Python	O(\|E\| log\|V\|)*	O(\|E\|)	Hard	variant of Cheapest Flights Within K Stops	`Dijkstra's Algorithm`
2039	The Time When the Network Becomes Idle	C++ Python	O(\|E\|)	O(\|E\|)	Medium		Math
2045	Second Minimum Time to Reach Destination	C++ Python	O(\|E\|)	O(\|E\|)	Hard		Bi-BFS
2050	Parallel Courses III	C++ Python	O(\|V\| + \|E\|)	O(\|E\|)	Hard	variant of Parallel Courses	Topological Sort
2059	Minimum Operations to Convert Number	C++ Python	O(m n)*	O(m)	Medium
2115	Find All Possible Recipes from Given Supplies	C++ Python	O(\|E\|)	O(\|E\|)	Medium		Topological Sort
2146	K Highest Ranked Items Within a Price Range	C++ Python	O(m n + klogk)*	O(m n)*	Medium		BFS, Quick Select, Sort
2258	Escape the Spreading Fire	C++ Python	O(m n)*	O(m n)*	Hard		BFS

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Depth-First Search

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1020	Number of Enclaves	C++ Python	O(m n)*	O(m n)*	Medium
1059	All Paths from Source Lead to Destination	C++ Python	O(n + e)	O(n + e)	Medium	🔒
1192	Critical Connections in a Network	C++ Python	O(\|V\| + \|E\|)	O(\|V\| + \|E\|)	Hard		`Tarjan's Algorithm`, `Bridge Finding Algorithm`
1202	Smallest String With Swaps	C++ Python	O(nlogn)	O(n)	Medium		Union Find
1254	Number of Closed Islands	C++ Python	O(m n)*	O(1)	Medium
1273	Delete Tree Nodes	C++ Python	O(n)	O(n)	Medium		DFS, DP
1315	Sum of Nodes with Even-Valued Grandparent	C++ Python	O(n)	O(h)	Medium
1319	Number of Operations to Make Network Connected	C++ Python	O(\|E\| + \|V\|)	O(\|V\|)	Medium		Union Find
1367	Linked List in Binary Tree	C++ Python	O(n + l)	O(h + l)	Medium		`KMP Algorithm`
1372	Longest ZigZag Path in a Binary Tree	C++ Python	O(n)	O(h)	Medium
1376	Time Needed to Inform All Employees	C++ Python	O(n)	O(n)	Medium
1377	Frog Position After T Seconds	C++ Python	O(n)	O(n)	Hard		DFS, Stack, BFS
1391	Check if There is a Valid Path in a Grid	C++ Python	O(m n)*	O(1)	Medium		Simulation
1466	Reorder Routes to Make All Paths Lead to the City Zero	C++ Python	O(n)	O(n)	Medium		DFS, Stack
1485	Clone Binary Tree With Random Pointer	C++ Python	O(n)	O(h)	Medium	🔒	DFS, Stack
1644	Lowest Common Ancestor of a Binary Tree II	C++ Python	O(n)	O(h)	Medium	🔒	DFS, Stack
1676	Lowest Common Ancestor of a Binary Tree IV	C++ Python	O(n)	O(h)	Medium	🔒	DFS, Stack
1722	Minimize Hamming Distance After Swap Operations	C++ Python	O(n)	O(n)	Medium		Flood Fill, Union Find
1740	Find Distance in a Binary Tree	C++ Python	O(n)	O(h)	Medium	variant of Lowest Common Ancestor of a Binary Tree, 🔒
1766	Tree of Coprimes	C++ Python	O(n)	O(n)	Hard
1905	Count Sub Islands	C++ Python	O(m n)*	O(1)	Medium		Flood Fill
1973	Count Nodes Equal to Sum of Descendants	C++ Python	O(n)	O(h)	Medium	🔒
2049	Count Nodes With the Highest Score	C++ Python	O(n)	O(n)	Medium
2065	Maximum Path Quality of a Graph	C++ Python	O(\|V\| + \|E\| + 4^10)	O(\|V\| + \|E\| )	Hard		Pruning
2192	All Ancestors of a Node in a Directed Acyclic Graph	C++ Python	O(\|V\| \|E\|)*	O(\|V\| + \|E\|)	Medium		DFS, BFS, Topological Sort
2246	Longest Path With Different Adjacent Characters	C++ Python	O(n)	O(h)	Hard		DFS, BFS, Topological Sort
2265	Count Nodes Equal to Average of Subtree	C++ Python	O(n)	O(h)	Medium		DFS, Tree

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Backtracking

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1087	Brace Expansion	C++ Python	O(p l * log(p * l))*	O(p l)*	Medium	🔒
1096	Brace Expansion II	C++ Python	O(p l * log(p * l))*	O(p l)*	Hard
1219	Path with Maximum Gold	C++ Python	O(m^2 n^2)*	O(m n)*	Medium
1240	Tiling a Rectangle with the Fewest Squares	C++ Python	O(n^2 m^2 * m^(n * m))*	O(n m)*	Hard
1255	Maximum Score Words Formed by Letters	C++ Python	O(n 2^n)*	O(n)	Hard
1258	Synonymous Sentences	C++ Python	O(p l * log(p * l))*	O(p l)*	Medium		Union Find
1307	Verbal Arithmetic Puzzle	C++ Python	O(10! n * l)*	O(n l)*	Hard
1379	Find a Corresponding Node of a Binary Tree in a Clone of That Tree	C++ Python	O(n)	O(h)	Medium		Stack
1593	Split a String Into the Max Number of Unique Substrings	C++ Python	O(n 2^(n - 1))*	O(n)	Medium
1659	Maximize Grid Happiness	C++ Python	O(C(m n, i) * C(m * n - i, e))*	O(min(m n, i + e))*	Hard		Pruning
1718	Construct the Lexicographically Largest Valid Sequence	C++ Python	O(n!)	O(b)	Medium		Backtracking
1723	Find Minimum Time to Finish All Jobs	C++ Python	O(k^n logr)*	O(n + k)	Hard		Backtracking, Pruning, Binary Search
1849	Splitting a String Into Descending Consecutive Values	C++ Python	O(n^2)	O(n)	Medium
1999	Smallest Greater Multiple Made of Two Digits	C++ Python	O(1)	O(1)	Medium	🔒	Backtracking, Bit Manipulation
2014	Longest Subsequence Repeated k Times	C++ Python	O(n (n/k)!)*	O(n/k)	Hard
2056	Number of Valid Move Combinations On Chessboard	C++ Python	O(1)	O(1)	Hard
2094	Finding 3-Digit Even Numbers	C++ Python	O(n)	O(1)	Easy

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Dynamic Programming

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1027	Longest Arithmetic Sequence	C++ Python	O(n^2)	O(n^2)	Medium
1035	Uncrossed Lines	C++ Python	O(m n)*	O(min(m, n))	Medium
1039	Minimum Score Triangulation of Polygon	C++ Python	O(n^3)	O(n^2)	Medium
1043	Partition Array for Maximum Sum	C++ Python	O(n k)*	O(k)	Medium
1048	Longest String Chain	C++ Python	O(n l^2)*	O(n l)*	Medium
1049	Last Stone Weight II	C++ Python	O(2^n)	O(2^n)	Medium
1066	Campus Bikes II	C++ Python	O(w b * 2^b)*	O(w b * 2^b)*	Medium	🔒
1092	Shortest Common Supersequence	C++ Python	O(m n)*	O(m n)*	Hard
1105	Filling Bookcase Shelves	C++ Python	O(n^2)	O(n)	Medium
1125	Smallest Sufficient Team	C++ Python	O(m 2^n)*	O(2^n)	Hard
1137	N-th Tribonacci Number	C++ Python	O(logn)	O(1)	Easy	variant of Fibonacci Number	Matrix Exponentiation
1139	Largest 1-Bordered Square	C++ Python	O(n^3)	O(n^2)	Medium
1140	Stone Game II	C++ Python	O(n(logn)^2)*	O(nlogn)	Medium
1143	Longest Common Subsequence	C++ Python	O(m n)*	O(min(m, n))	Medium
1155	Number of Dice Rolls With Target Sum	C++ Python	O(d f * t)*	O(t)	Medium
1182	Shortest Distance to Target Color	C++ Python	O(n)	O(n)	Medium	🔒
1186	Maximum Subarray Sum with One Deletion	C++ Python	O(n)	O(1)	Medium
1187	Make Array Strictly Increasing	C++ Python	O(n^2 logn)*	O(n)	Hard
1191	K-Concatenation Maximum Sum	C++ Python	O(n)	O(1)	Medium
1216	Valid Palindrome III	C++ Python	O(n^2)	O(n)	Hard	🔒, variant of Longest Palindromic Subsequence
1218	Longest Arithmetic Subsequence of Given Difference	C++ Python	O(n)	O(n)	Medium
1220	Count Vowels Permutation	C++ Python	O(logn)	O(1)	Hard		Matrix Exponentiation
1223	Dice Roll Simulation	C++ Python	O(m n)*	O(m)	Medium
1230	Toss Strange Coins	C++ Python	O(n^2)	O(n)	Medium
1235	Maximum Profit in Job Scheduling	C++ Python	O(nlogn)	O(n)	Hard		DP, Heap
1239	Maximum Length of a Concatenated String with Unique Characters	C++ Python	O(n) ~ O(2^n)	O(1) ~ O(2^n)	Medium		DP, Bit Manipulation
1246	Palindrome Removal	C++ Python	O(n^3)	O(n^2)	Hard
1262	Greatest Sum Divisible by Three	C++ Python	O(n)	O(1)	Medium
1269	Number of Ways to Stay in the Same Place After Some Steps	C++ Python	O(n^2)	O(n)	Hard
1277	Count Square Submatrices with All Ones	C++ Python	O(m n)*	O(1)	Medium
1278	Palindrome Partitioning III	C++ Python	O(k n^2)*	O(n^2)	Hard
1289	Minimum Falling Path Sum II	C++ Python	O(m n)*	O(1)	Hard
1292	Maximum Side Length of a Square with Sum Less than or Equal to Threshold	C++ Python	O(m n * log(min(m, n)))*	O(m n)*	Medium		Binary Search
1301	Number of Paths with Max Score	C++ Python	O(n^2)	O(n)	Hard
1312	Minimum Insertion Steps to Make a String Palindrome	C++ Python	O(n^2)	O(n)	Hard	variant of Longest Common Subsequence
1314	Matrix Block Sum	C++ Python	O(m n)*	O(m n)*	Medium	variant of Range Sum Query 2D - Immutable
1320	Minimum Distance to Type a Word Using Two Fingers	C++ Python	O(n)	O(1)	Hard
1335	Minimum Difficulty of a Job Schedule	C++ Python	O(d n^2)*	O(d n)*	Hard
1340	Jump Game V	C++ Python	O(n)	O(n)	Hard		Sliding Window, Mono Stack, Segment Tree
1387	Sort Integers by The Power Value	C++ Python	O(n) on average	O(n)	Medium		Quick Select
1388	Pizza With 3n Slices	C++ Python	O(n^2)	O(n)	Hard	variant of House Robber II
1395	Count Number of Teams	C++ Python	O(n^2)	O(1)	Medium
1397	Find All Good Strings	C++ Python	O(m n)*	O(m)	Hard		`KMP Algorithm`
1406	Stone Game III	C++ Python	O(n)	O(1)	Hard
1411	Number of Ways to Paint N × 3 Grid	C++ Python	O(logn)	O(1)	Hard		Matrix Exponentiation
1416	Restore The Array	C++ Python	O(nlogk)	O(logk)	Hard
1420	Build Array Where You Can Find The Maximum Exactly K Comparisons	C++ Python	O(n m * k)*	O(m k)*	Hard
1434	Number of Ways to Wear Different Hats to Each Other	C++ Python	O(h 2^n)*	O(2^n)	Hard
1444	Number of Ways of Cutting a Pizza	C++ Python	O(m n * k * (m + n))*	O(m n * k)*	Hard
1449	Form Largest Integer With Digits That Add up to Target	C++ Python	O(t)	O(t)	Hard
1458	Max Dot Product of Two Subsequences	C++ Python	O(m n)*	O(min(m, n))	Hard
1463	Cherry Pickup II	C++ Python	O(m n^2)*	O(n^2)	Hard
1467	Probability of a Two Boxes Having The Same Number of Distinct Balls	C++ Python	O(k^3 n^2)*	O(k^2 n)*	Hard		Binomial Coefficients
1473	Paint House III	C++ Python	O(m t * n^2)*	O(t n)*	Hard
1477	Find Two Non-overlapping Sub-arrays Each With Target Sum	C++ Python	O(n)	O(n)	Medium
1478	Allocate Mailboxes	C++ Python	O(m n^2)*	O(n)	Hard		DP, Math, Median
1494	Parallel Courses II	C++ Python	O((n C(c, min(c, k))) * 2^n)*	O(2^n)	Hard		Combinations
1504	Count Submatrices With All Ones	C++ Python	O(m n)*	O(n)	Medium		Mono Stack
1510	Stone Game IV	C++ Python	O(n sqrt(n))*	O(n)	Hard
1524	Number of Sub-arrays With Odd Sum	C++ Python	O(n)	O(1)	Medium
1531	String Compression II	C++ Python	O(n^2 k)*	O(n k)*	Hard
1547	Minimum Cost to Cut a Stick	C++ Python	O(n^3)	O(n^2)	Hard
1548	The Most Similar Path in a Graph	C++ Python	O(n^ m)*	O(n m)*	Hard	🔒
1553	Minimum Number of Days to Eat N Oranges	C++ Python	O((logn)^2)	O((logn)^2)	Hard
1563	Stone Game V	C++ Python	O(n^2)	O(n^2)	Hard
1569	Number of Ways to Reorder Array to Get Same BST	C++ Python	O(n^2)	O(n^2)	Hard		DFS
1575	Count All Possible Routes	C++ Python	O(nlogn + n f)*	O(n f)*	Hard		Math
1594	Maximum Non Negative Product in a Matrix	C++ Python	O(m n)*	O(n)	Medium
1595	Minimum Cost to Connect Two Groups of Points	C++ Python	O(m n * 2^n)*	O(2^n)	Hard
1617	Count Subtrees With Max Distance Between Cities	C++ Python	O(n^6)	O(n^3)	Hard		Backtracking, Graph
1626	Best Team With No Conflicts	C++ Python	O(nloga)	O(n)	Medium	variant of Longest Increasing Subsequence	Sort, DP, Segment Tree
1639	Number of Ways to Form a Target String Given a Dictionary	C++ Python	O(l (w + n))*	O(n)	Hard
1655	Distribute Repeating Integers	C++ Python	O(n + m 3^m)*	O(n + 2^m)	Hard		Submask Enumeration
1664	Ways to Make a Fair Array	C++ Python	O(n)	O(1)	Medium		Prefix Sum
1681	Minimum Incompatibility	C++ Python	O(max(n 2^n, 3^n))*	O(2^n)	Hard		Combinations, Backtracking, Submask Enumeration
1682	Longest Palindromic Subsequence II	C++ Python	O(n^2)	O(n)	Medium	🔒
1690	Stone Game VII	C++ Python	O(n^2)	O(n)	Medium
1691	Maximum Height by Stacking Cuboids	C++ Python	O(n^2)	O(n)	Hard
1692	Count Ways to Distribute Candies	C++ Python	O(n k)*	O(k)	Hard	🔒
1745	Palindrome Partitioning IV	C++ Python	O(n^2)	O(n)	Hard		DP, `Manacher's Algorithm`
1746	Maximum Subarray Sum After One Operation	C++ Python	O(n)	O(1)	Medium	variant of Maximum Subarray, 🔒
1751	Maximum Number of Events That Can Be Attended II	C++ Python	O(nlogn + n k)*	O(n k)*	Hard		Binary Search
1770	Maximum Score from Performing Multiplication Operations	C++ Python	O(m^2)	O(m)	Medium
1771	Maximize Palindrome Length From Subsequences	C++ Python	O((m + n)^2)	O((m + n)^2)	Hard
1774	Closest Dessert Cost	C++ Python	O(m t)*	O(t)	Medium
1787	Make the XOR of All Segments Equal to Zero	C++ Python	O(n + k m)*	O(min(k m, n))*	Hard
1799	Maximize Score After N Operations	C++ Python	O(n^2 2^n)*	O(2^n)	Hard
1803	Count Pairs With XOR in a Range	C++ Python	O(n)	O(n)	Hard		DP, Trie
1857	Largest Color Value in a Directed Graph	C++ Python	O(n + m)	O(n + m)	Hard		DP, Topological Sort
1866	Number of Ways to Rearrange Sticks With K Sticks Visible	C++ Python	O(n k)*	O(k)	Hard
1871	Jump Game VII	C++ Python	O(n)	O(n)	Medium		Line Sweep, DP, BFS
1872	Stone Game VIII	C++ Python	O(n)	O(1)	Hard
1883	Minimum Skips to Arrive at Meeting On Time	C++ Python	O(n^2)	O(n)	Hard
1896	Minimum Cost to Change the Final Value of Expression	C++ Python	O(n)	O(n)	Hard		Stack, DP
1900	The Earliest and Latest Rounds Where Players Compete	C++ Python	O(n^4)	O(n^2)	Hard
1908	Game of Nim	C++ Python	O(n)	O(1)	Medium	🔒
1931	Painting a Grid With Three Different Colors	C++ Python	O(2^(3 m) * logn)*	O(2^(2 m))*	Hard	variant of Number of Ways to Paint N × 3 Grid	DP, Backtracking, Matrix Exponentiation, State Compression
1937	Maximum Number of Points with Cost	C++ Python	O(m n)*	O(n)	Medium		Prefix Sum
1955	Count Number of Special Subsequences	C++ Python	O(n)	O(1)	Hard
1959	Minimum Total Space Wasted With K Resizing Operations	C++ Python	O(k n^2)*	O(k n)*	Medium
1960	Maximum Product of the Length of Two Palindromic Substrings	C++ Python	O(n)	O(n)	Hard		`Manacher's Algorithm`, DP
1977	Number of Ways to Separate Numbers	C++ Python	O(n^2)	O(n^2)	Hard		DP
1981	Minimize the Difference Between Target and Chosen Elements	C++ Python	O(t m * n)*	O(t)	Medium		DP, Pruning
1986	Minimum Number of Work Sessions to Finish the Tasks	C++ Python	O(n 2^n)*	O(2^n)	Medium		DP
1987	Number of Unique Good Subsequences	C++ Python	O(n)	O(1)	Hard	variant of Distinct Subsequences II	DP
1994	The Number of Good Subsets	C++ Python	O(n 2^p)*	O(2^p)	Hard		DP, `Sieve of Eratosthenes`
1997	First Day Where You Have Been in All the Rooms	C++ Python	O(n)	O(n)	Medium		DP
2002	Maximum Product of the Length of Two Palindromic Subsequences	C++ Python	O(3^n)	O(2^n)	Medium		DP, Submask Enumeration
2008	Maximum Earnings From Taxi	C++ Python	O(n + mlogm)	O(n)	Medium		DP
2019	The Score of Students Solving Math Expression	C++ Python	O(n^3 a^2)*	O(n^2)	Hard	variant of Burst Balloons
2031	Count Subarrays With More Ones Than Zeros	C++ Python	O(n)	O(n)	Medium	🔒	Prefix Sum, DP
2044	Count Number of Maximum Bitwise-OR Subsets	C++ Python	O(min(2^n, m n))*	O(min(2^n, m))	Medium		DP
2052	Minimum Cost to Separate Sentence Into Rows	C++ Python	O(s + n k)*	O(k)	Medium	🔒	DP
2060	Check if an Original String Exists Given Two Encoded Strings	C++ Python	O(m n * k)*	O(min(m, n) k)*	Hard		DP, Memoization
2088	Count Fertile Pyramids in a Land	C++ Python	O(m n)*	O(n)	Hard		DP
2140	Solving Questions With Brainpower	C++ Python	O(n)	O(n)	Medium		DP
2143	Choose Numbers From Two Arrays in Range	C++ Python	O(n^2 v)*	O(n v)*	Hard	🔒	DP
2167	Minimum Time to Remove All Cars Containing Illegal Goods	C++ Python	O(n)	O(1)	Hard		DP
2174	Remove All Ones With Row and Column Flips II	C++ Python	O((m n) * 2^(m * n))*	O(2^(m n))*	Medium	🔒	DP, Bitmasks
2184	Number of Ways to Build Sturdy Brick Wall	C++ Python	O(h p^2)*	O(p^2)	Medium	🔒, variant of Painting a Grid With Three Different Colors	DP, Backtracking, Matrix Exponentiation
2188	Minimum Time to Finish the Race	C++ Python	O((n + l) logc)*	O(n + l + logc)	Hard		Greedy, DP
2189	Number of Ways to Build House of Cards	C++ Python	O(n^2)	O(n)	Medium	🔒	DP
2209	Minimum White Tiles After Covering With Carpets	C++ Python	O(m n)*	O(m n)*	Hard		DP
2218	Maximum Value of K Coins From Piles	C++ Python	O(min(n k^2, m * k)))*	O(k)	Hard		DP
2222	Number of Ways to Select Buildings	C++ Python	O(n)	O(1)	Medium		DP
2247	Maximum Cost of Trip With K Highways	C++ Python	O(n^2 2^n)*	O(n 2^n)*	Hard	🔒	DP, Bitmasks, BFS
2266	Count Number of Texts	C++ Python	O(n)	O(1)	Medium		DP
2267	Check if There Is a Valid Parentheses String Path	C++ Python	O(m n)*	O(n)	Hard		DP, Bitsets

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Greedy

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1005	Maximize Sum Of Array After K Negations	C++ Python	O(n) on average	O(1)	Easy		Quick Select
1024	Video Stitching	C++ Python	O(nlogn)	O(1)	Medium	variant of Jump Game II
1029	Two City Scheduling	C++ Python	O(n) on average	O(1)	Easy		Quick Select
1053	Previous Permutation With One Swap	C++ Python	O(n)	O(1)	Medium
1055	Shortest Way to Form String	C++ Python	O(m + n)	O(m)	Medium	🔒, variant of Minimum Window Subsequence
1058	Minimize Rounding Error to Meet Target	C++ Python	O(n) on average	O(n)	Medium	🔒	Quick Select
1081	Smallest Subsequence of Distinct Characters	C++ Python	O(n)	O(1)	Medium	same as Remove Duplicate Letters	Mono Stack
1090	Largest Values From Labels	C++ Python	O(nlogn)	O(n)	Medium
1111	Maximum Nesting Depth of Two Valid Parentheses Strings	C++ Python	O(n)	O(1)	Medium
1163	Last Substring in Lexicographical Order	C++ Python	O(n)	O(1)	Hard
1167	Minimum Cost to Connect Sticks	C++ Python	O(nlogn)	O(n)	Medium	🔒
1183	Maximum Number of Ones	C++ Python	O(1)	O(1)	Hard	🔒
1196	How Many Apples Can You Put into the Basket	C++ Python	O(nlogn)	O(n)	Easy	🔒
1199	Minimum Time to Build Blocks	C++ Python	O(nlogn)	O(n)	Hard	🔒
1221	Split a String in Balanced Strings	C++ Python	O(n)	O(1)	Easy
1247	Minimum Swaps to Make Strings Equal	C++ Python	O(n)	O(1)	Easy
1249	Minimum Remove to Make Valid Parentheses	C++ Python	O(n)	O(1)	Medium		Stack
1253	Reconstruct a 2-Row Binary Matrix	C++ Python	O(n)	O(1)	Medium
1272	Remove Interval	C++ Python	O(n)	O(1)	Medium		Line Sweep
1282	Group the People Given the Group Size They Belong To	C++ Python	O(n)	O(n)	Medium
1288	Remove Covered Intervals	C++ Python	O(nlogn)	O(1)	Medium		Line Sweep
1296	Divide Array in Sets of K Consecutive Numbers	C++ Python	O(nlogn)	O(n)	Medium
1326	Minimum Number of Taps to Open to Water a Garden	C++ Python	O(n)	O(n)	Hard	variant of Jump Game II
1338	Reduce Array Size to The Half	C++ Python	O(n)	O(n)	Medium		Counting Sort
1353	Maximum Number of Events That Can Be Attended	C++ Python	O(r + nlogn)	O(n)	Medium		Heap, Sort
1354	Construct Target Array With Multiple Sums	C++ Python	O(log(max(t)) logn)*	O(n)	Hard		Heap
1386	Cinema Seat Allocation	C++ Python	O(n)	O(n)	Medium
1400	Construct K Palindrome Strings	C++ Python	O(n)	O(1)	Medium
1402	Reducing Dishes	C++ Python	O(nlogn)	O(1)	Hard
1403	Minimum Subsequence in Non-Increasing Order	C++ Python	O(nlogn)	O(1)	Easy
1405	Longest Happy String	C++ Python	O(n)	O(1)	Medium
1414	Find the Minimum Number of Fibonacci Numbers Whose Sum Is K	C++ Python	O(logk)	O(1)	Medium
1419	Minimum Number of Frogs Croaking	C++ Python	O(n)	O(1)	Medium
1433	Check If a String Can Break Another String	C++ Python	O(n)	O(1)	Medium
1488	Avoid Flood in The City	C++ Python	O(nlogn)	O(n)	Medium
1518	Water Bottles	C++ Python	O(logn/logm)	O(1)	Easy
1520	Maximum Number of Non-Overlapping Substrings	C++ Python	O(n)	O(1)	Medium
1526	Minimum Number of Increments on Subarrays to Form a Target Array	C++ Python	O(n)	O(1)	Hard
1536	Minimum Swaps to Arrange a Binary Grid	C++ Python	O(n^2)	O(1)	Medium
1546	Maximum Number of Non-Overlapping Subarrays With Sum Equals Target	C++ Python	O(n)	O(n)	Medium
1564	Put Boxes Into the Warehouse I	C++ Python	O(nlogn)	O(1)	Medium	🔒
1567	Maximum Length of Subarray With Positive Product	C++ Python	O(n)	O(1)	Medium
1568	Minimum Number of Days to Disconnect Island	C++ Python	O(m^2 n^2)*	O(m n)*	Medium		DFS
1578	Minimum Deletion Cost to Avoid Repeating Letters	C++ Python	O(n)	O(1)	Medium
1580	Put Boxes Into the Warehouse II	C++ Python	O(nlogn)	O(1)	Medium	🔒
1585	Check If String Is Transformable With Substring Sort Operations	C++ Python	O(n)	O(n)	Hard
1589	Maximum Sum Obtained of Any Permutation	C++ Python	O(nlogn)	O(n)	Medium
1591	Strange Printer II	C++ Python	O(c m * n + e)*	O(e)	Hard
1599	Maximum Profit of Operating a Centennial Wheel	C++ Python	O(n)	O(1)	Medium
1605	Find Valid Matrix Given Row and Column Sums	C++ Python	O(m + n)	O(1)	Medium
1616	Split Two Strings to Make Palindrome	C++ Python	O(n)	O(1)	Medium		Two Pointers
1632	Rank Transform of a Matrix	C++ Python	O(m n * log(m * n))*	O(m n)*	Hard		Union Find
1647	Minimum Deletions to Make Character Frequencies Unique	C++ Python	O(n)	O(1)	Medium
1653	Minimum Deletions to Make String Balanced	C++ Python	O(n)	O(1)	Medium
1663	Smallest String With A Given Numeric Value	C++ Python	O(n)	O(1)	Medium
1665	Minimum Initial Energy to Finish Tasks	C++ Python	O(nlogn)	O(1)	Hard
1673	Find the Most Competitive Subsequence	C++ Python	O(n)	O(k)	Meidum		Stack, Greedy
1674	Minimum Moves to Make Array Complementary	C++ Python	O(n + k)	O(k)	Meidum
1686	Stone Game VI	C++ Python	O(nlogn)	O(n)	Medium
1689	Partitioning Into Minimum Number Of Deci-Binary Numbers	C++ Python	O(n)	O(1)	Medium
1702	Maximum Binary String After Change	C++ Python	O(n)	O(1)	Medium
1705	Maximum Number of Eaten Apples	C++ Python	O(nlogn)	O(n)	Medium		Heap
1708	Largest Subarray Length K	C++ Python	O(n)	O(1)	Easy	🔒, variant of Last Substring in Lexicographical Order
1710	Maximum Units on a Truck	C++ Python	O(nlogn)	O(1)	Easy
1717	Maximum Score From Removing Substrings	C++ Python	O(n)	O(1)	Medium
1725	Number Of Rectangles That Can Form The Largest Square	C++ Python	O(n)	O(1)	Easy
1727	Largest Submatrix With Rearrangements	C++ Python	O(m nlogn)*	O(1)	Medium		Sort
1733	Minimum Number of People to Teach	C++ Python	O(n m^2)*	O(n m)*	Medium
1736	Latest Time by Replacing Hidden Digits	C++ Python	O(1)	O(1)	Easy
1737	Change Minimum Characters to Satisfy One of Three Conditions	C++ Python	O(m + n)	O(1)	Medium		Prefix Sum
1749	Maximum Absolute Sum of Any Subarray	C++ Python	O(n)	O(1)	Medium	variant of Maximum Subarray	Prefix Sum
1754	Largest Merge Of Two Strings	C++ Python	O(m n)*	O(m + n)	Medium
1758	Minimum Changes To Make Alternating Binary String	C++ Python	O(n)	O(1)	Easy
1759	Count Number of Homogenous Substrings	C++ Python	O(n)	O(1)	Medium
1762	Buildings With an Ocean View	C++ Python	O(n)	O(1)	Medium	🔒
1764	Form Array by Concatenating Subarrays of Another Array	C++ Python	O(n)	O(n)	Medium		`KMP Algorithm`
1769	Minimum Number of Operations to Move All Balls to Each Box	C++ Python	O(n)	O(1)	Medium
1775	Equal Sum Arrays With Minimum Number of Operations	C++ Python	O(m + n)	O(1)	Medium
1785	Minimum Elements to Add to Form a Given Sum	C++ Python	O(n)	O(1)	Medium
1788	Maximize the Beauty of the Garden	C++ Python	O(n)	O(n)	Hard	🔒
1793	Maximum Score of a Good Subarray	C++ Python	O(n)	O(1)	Hard		Greedy, Prefix Sum. Binary Search
1794	Count Pairs of Equal Substrings With Minimum Difference	C++ Python	O(n)	O(1)	Medium	🔒
1798	Maximum Number of Consecutive Values You Can Make	C++ Python	O(nlogn)	O(1)	Medium
1801	Number of Orders in the Backlog	C++ Python	O(nlogn)	O(n)	Medium		Greedy, Heap
1815	Maximum Number of Groups Getting Fresh Donuts	C++ Python	O((b/2) (n/(b/2)+1)^(b/2))*	O((n/(b/2)+1)^(b/2))	Hard		Greedy, DP
1824	Minimum Sideway Jumps	C++ Python	O(n)	O(1)	Medium		Greedy, DP
1827	Minimum Operations to Make the Array Increasing	C++ Python	O(n)	O(1)	Easy
1833	Maximum Ice Cream Bars	C++ Python	O(nlogn)	O(1)	Medium
1840	Maximum Building Height	C++ Python	O(nlogn)	O(1)	Hard
1842	Next Palindrome Using Same Digits	C++ Python	O(n)	O(1)	Hard	🔒
1846	Maximum Element After Decreasing and Rearranging	C++ Python	O(nlogn)	O(1)	Medium
1850	Minimum Adjacent Swaps to Reach the Kth Smallest Number	C++ Python	O((k + n) n)*	O(n)	Medium
1864	Minimum Number of Swaps to Make the Binary String Alternating	C++ Python	O(n)	O(1)	Medium
1874	Minimize Product Sum of Two Arrays	C++ Python	O(nlogn)	O(1)	Medium	GCJ2008 - Round 1A, 🔒
1877	Minimize Maximum Pair Sum in Array	C++ Python	O(nlogn)	O(1)	Medium
1881	Maximum Value after Insertion	C++ Python	O(n)	O(1)	Medium
1887	Reduction Operations to Make the Array Elements Equal	C++ Python	O(nlogn)	O(1)	Medium		Sort
1893	Check if All the Integers in a Range Are Covered	C++ Python	O(n + r)	O(r)	Easy		Line Sweep, Sort
1894	Find the Student that Will Replace the Chalk	C++ Python	O(n)	O(1)	Medium
1897	Redistribute Characters to Make All Strings Equal	C++ Python	O(n)	O(1)	Easy
1899	Merge Triplets to Form Target Triplet	C++ Python	O(n)	O(1)	Medium
1911	Maximum Alternating Subsequence Sum	C++ Python	O(n)	O(1)	Medium	variant of Best Time to Buy and Sell Stock II
1913	Maximum Product Difference Between Two Pairs	C++ Python	O(n)	O(1)	Medium
1921	Eliminate Maximum Number of Monsters	C++ Python	O(nlogn)	O(1)	Medium
1927	Sum Game	C++ Python	O(n)	O(1)	Medium
1936	Add Minimum Number of Rungs	C++ Python	O(n)	O(1)	Medium
1946	Largest Number After Mutating Substring	C++ Python	O(n)	O(1)	Medium
1953	Maximum Number of Weeks for Which You Can Work	C++ Python	O(n)	O(1)	Medium
1975	Maximum Matrix Sum	C++ Python	O(n^2)	O(1)	Medium
2027	Minimum Moves to Convert String	C++ Python	O(n)	O(1)	Easy
2030	Smallest K-Length Subsequence With Occurrences of a Letter	C++ Python	O(n)	O(n)	Hard		Mono Stack, Greedy
2036	Maximum Alternating Subarray Sum	C++ Python	O(n)	O(1)	Medium	variant of Maximum Alternating Subsequence Sum, 🔒	Greedy, `Kadane's Algorithm`
2037	Minimum Number of Moves to Seat Everyone	C++ Python	O(nlogn)	O(1)	Easy		Greedy
2071	Maximum Number of Tasks You Can Assign	C++ Python	O(n (logn)^2)*	O(n)	Hard		Greedy, Binary Search, Sorted List
2086	Minimum Number of Buckets Required to Collect Rainwater from Houses	C++ Python	O(n)	O(1)	Medium		Greedy
2087	Minimum Cost Homecoming of a Robot in a Grid	C++ Python	O(m + n)	O(1)	Medium		Greedy
2126	Destroying Asteroids	C++ Python	O(nlogn)	O(1)	Medium		Greedy
2136	Earliest Possible Day of Full Bloom	C++ Python	O(nlogn)	O(n)	Hard		Greedy
2139	Minimum Moves to Reach Target Score	C++ Python	O(logn)	O(1)	Medium
2141	Maximum Running Time of N Computers	C++ Python	O(nlogm)	O(1)	Hard		Greedy, Binary Search
2144	Minimum Cost of Buying Candies With Discount	C++ Python	O(nlogn)	O(1)	Easy		Greedy, Sort
2147	Number of Ways to Divide a Long Corridor	C++ Python	O(n)	O(1)	Hard		Greedy, Combinatorics
2160	Minimum Sum of Four Digit Number After Splitting Digits	C++ Python	O(1)	O(1)	Easy		Greedy
2165	Smallest Value of the Rearranged Number	C++ Python	O(d)	O(d)	Medium		Greedy, Counting Sort
2178	Maximum Split of Positive Even Integers	C++ Python	O(sqrt(n))	O(1)	Medium		Greedy
2182	Construct String With Repeat Limit	C++ Python	O(n)	O(1)	Medium		Greedy
2193	Minimum Number of Moves to Make Palindrome	C++ Python	O(nlogn)	O(n)	Hard		Greedy, BIT, Fenwick Tree
2195	Append K Integers With Minimal Sum	C++ Python	O(nlogn)	O(n)	Medium		Greedy
2207	Maximize Number of Subsequences in a String	C++ Python	O(n)	O(1)	Medium		Counting, Greedy
2214	Minimum Health to Beat Game	C++ Python	O(n)	O(1)	Medium	🔒	Greedy
2216	Minimum Deletions to Make Array Beautiful	C++ Python	O(n)	O(1)	Medium		Greedy
2224	Minimum Number of Operations to Convert Time	C++ Python	O(1)	O(1)	Easy		Greedy
2259	Remove Digit From Number to Maximize Result	C++ Python	O(n)	O(1)	Easy		Greedy
2263	Make Array Non-decreasing or Non-increasing	C++ Python	O(nlogn)	O(n)	Hard	🔒	DP, Greedy, Heap
2268	Minimum Number of Keypresses	C++ Python	O(n)	O(1)	Medium	🔒	Greedy, Sort

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Graph

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1042	Flower Planting With No Adjacent	C++ Python	O(n)	O(n)	Easy
1101	The Earliest Moment When Everyone Become Friends	C++ Python	O(nlogn)	O(n)	Medium	🔒	Union Find
1135	Connecting Cities With Minimum Cost	C++ Python	O(nlogn)	O(n)	Medium	🔒	Union Find, `Kruskal's Algorithm`, MST
1168	Optimize Water Distribution in a Village	C++ Python	O(nlogn)	O(n)	Hard	🔒	Union Find
1334	Find the City With the Smallest Number of Neighbors at a Threshold Distance	C++ Python	O(n^3)	O(n^2)	Medium		`Floyd-Warshall Algorithm`
1349	Maximum Students Taking Exam	C++ Python	O(m n * sqrt(m * n))*	O(m + n)	Hard	GCJ2008 - Round 3	`Hopcroft-Karp Bipartite Matching`, `Hungarian Bipartite Matching`, Maximum Independent Set
1361	Validate Binary Tree Nodes	C++ Python	O(n)	O(n)	Medium		DFS, Tree
1462	Course Schedule IV	C++ Python	O(n^3)	O(n^2)	Medium		`Floyd-Warshall Algorithm`
1489	Find Critical and Pseudo-Critical Edges in Minimum Spanning Tree	C++ Python	O(nlogn)	O(n)	Hard		`Kruskal Algorithm`
1557	Minimum Number of Vertices to Reach All Nodes	C++ Python	O(e)	O(n)	Medium
1579	Remove Max Number of Edges to Keep Graph Fully Traversable	C++ Python	O(n + m)	O(n)	Hard		Union Find
1584	Min Cost to Connect All Points	C++ Python	O(n^2)	O(n)	Medium		Union Find, `Kruskal's Algorithm`, MST
1601	Maximum Number of Achievable Transfer Requests	C++ Python	O((n + r) 2^r)*	O(n + r)	Hard		Combinations, Backtracking
1615	Maximal Network Rank	C++ Python	O(m + n + k^2)	O(m + n)	Medium		Counting Sort
1627	Graph Connectivity With Threshold	C++ Python	O(nlogn + q)	O(n)	Hard		Union Find, Math
1631	Path With Minimum Effort	C++ Python	O(m n * log(m * n))*	O(m n)*	Medium		Binary Search, DFS, BFS, Bi-BFS, Union Find, `Dijkstra's Algorithm`
1697	Checking Existence of Edge Length Limited Paths	C++ Python	O(nlogn + mlogm)	O(n)	Hard		Union Find
1719	Number Of Ways To Reconstruct A Tree	C++ Python	O(nlogn)	O(n)	Hard
1724	Checking Existence of Edge Length Limited Paths II	C++ Python	ctor: O(nlogn + mlogm) query: O(logn)	O(nlogn + m)	Hard	🔒	Versioned Union Find, Binary Lifting
1743	Restore the Array From Adjacent Pairs	C++ Python	O(n)	O(n)	Medium
1761	Minimum Degree of a Connected Trio in a Graph	C++ Python	O(n^3)	O(n^2)	Hard
1778	Shortest Path in a Hidden Grid	C++ Python	O(m n)*	O(m n)*	Medium	🔒	DFS, BFS, Bi-BFS
1782	Count Pairs Of Nodes	C++ Python	O(n + e + q)	O(n + e)	Hard		Counting, Two Pointers
1786	Number of Restricted Paths From First to Last Node	C++ Python	O(\|E\| log\|V\|)*	O(\|E\|)	Medium		`Dijkstra's Algorithm`, DP
1791	Find Center of Star Graph	C++ Python	O(n)	O(n)	Medium
1810	Minimum Path Cost in a Hidden Grid	C++ Python	O(m n * log(m * n))*	O(m n)*	Medium	🔒	DFS, `Dijkstra's Algorithm`
1820	Maximum Number of Accepted Invitations	C++ Python	O(m n * sqrt(m + n))*	O(m + n)	Medium	🔒	`Hopcroft-Karp Bipartite Matching`, `Hungarian Bipartite Matching`
1879	Minimum XOR Sum of Two Arrays	C++ Python	O(n^3)	O(n^2)	Hard		DP, `Hungarian Weighted Bipartite Matching`
1947	Maximum Compatibility Score Sum	C++ Python	O(m^2 (n + m))*	O(m^2)	Medium	variant of Minimum XOR Sum of Two Arrays	DP, `Hungarian Weighted Bipartite Matching`
1971	Find if Path Exists in Graph	C++ Python	O(\|V\| + \|E\|)	O(\|V\| + \|E\|)	Easy		DFS, BFS, Bi-BFS
1976	Number of Ways to Arrive at Destination	C++ Python	O(\|E\| log\|V\|)*	O(\|E\|)	Medium		`Dijkstra's Algorithm`
2076	Process Restricted Friend Requests	C++ Python	O(n r)*	O(n)	Hard		Union Find
2077	Paths in Maze That Lead to Same Room	C++ Python	O(\|V\|^3)	O(\|E\|)	Medium	🔒
2092	Find All People With Secret	C++ Python	O(nlogn)	O(nlogn)	Hard		BFS, DFS, Union Find
2093	Minimum Path Cost in a Hidden Grid	C++ Python	O(\|E\| log\|V\|)*	O(\|V\| + \|E\|)	Medium	variant of Cheapest Flights Within K Stops, 🔒	`Dijkstra's Algorithm`, DP
2097	Valid Arrangement of Pairs	C++ Python	O(\|V\| + \|E\|)	O(\|V\| + \|E\|)	Hard	variant of Reconstruct Itinerary	`Hierholzer's Algorithm`, Eulerian Path
2123	Minimum Operations to Remove Adjacent Ones in Matrix	C++ Python	O(m n * sqrt(m * n))*	O(m + n)	Hard	variant of Maximum Students Taking Exam, 🔒	`Hopcroft-Karp Bipartite Matching`, Maximum Independent Set
2127	Maximum Employees to Be Invited to a Meeting	C++ Python	O(n)	O(n)	Hard
2172	Maximum AND Sum of Array	C++ Python	O(n^3)	O(n^2)	Hard	variant of Maximum Compatibility Score Sum	DP, `Hungarian Weighted Bipartite Matching`
2203	Minimum Weighted Subgraph With the Required Paths	C++ Python	O(\|E\| log\|V\|)*	O(\|E\|)	Hard		`Dijkstra's Algorithm`
2204	Distance to a Cycle in Undirected Graph	C++ Python	O(\|V\| + \|E\|)	O(\|V\| + \|E\|)	Hard	🔒	Graph, DFS, BFS
2242	Maximum Score of a Node Sequence	C++ Python	O(\|V\| + \|E\|)	O(\|V\|)	Hard		Graph

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Geometry

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1453	Maximum Number of Darts Inside of a Circular Dartboard	C++ Python	O(n^2 logn)*	O(n)	Hard		Line Sweep
1515	Best Position for a Service Centre	C++ Python	O(n iter)*	O(n)	Hard		Geometric Median, Gradient Descent, Weiszfeld's Algorithm
1610	Maximum Number of Visible Points	C++ Python	O(nlogn)	O(n)	Hard		Two Pointers, Sliding Window
1924	Erect the Fence II	C++ Python	O(n) on average	O(n)	Hard	🔒	`Welzl's Algorithm`
1956	Minimum Time For K Virus Variants to Spread	C++ Python	O(nlogn logr)*	O(n)	Hard	🔒	Geometry, Binary Search, Line Sweep, Segment Tree, Coordinate Compression
2101	Detonate the Maximum Bombs	C++ Python	O(\|V\|^2 + \V\| \|E\|)*	O(\V\| + \|E\|)	Medium		Graph, DFS, BFS

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Simulation

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1138	Alphabet Board Path	C++ Python	O(n)	O(1)	Medium
1243	Array Transformation	C++ Python	O(n^2)	O(n)	Easy
2061	Number of Spaces Cleaning Robot Cleaned	C++ Python	O(m n)*	O(1)	Medium	🔒
2162	Minimum Cost to Set Cooking Time	C++ Python	O(1)	O(1)	Medium
2257	Count Unguarded Cells in the Grid	C++ Python	O(m n)*	O(m n)*	Medium		Array, Simulation

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Design

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1146	Snapshot Array	C++ Python	set: O(1) get: O(logn)	O(n)	Medium
1166	Design File System	C++ Python	create: O(n) get: O(n)	O(n)	Medium	🔒
1172	Dinner Plate Stacks	C++ Python	push: O(logn) pop: O(1), amortized popAtStack: (logn)	O(n c)*	Hard
1206	Design Skiplist	C++ Python	O(logn), on average	O(n)	Hard
1236	Web Crawler	C++ Python	O(\|V\| + \|E\|)	O(\|V\|)	Medium	🔒	BFS, DFS
1244	Design A Leaderboard	C++ Python	ctor: O(1) add: O(1) top: O(n) reset: O(1)	O(n)	Medium
1268	Search Suggestions System	C++ Python	ctor: O(n l)* suggest: O(l^2)	O(t)	Medium		Trie
1286	Iterator for Combination	C++ Python	O(k)	O(k)	Medium		Stack
1348	Tweet Counts Per Frequency	C++ Python	add: O(logn) query: O(c)	O(n)	Medium
1352	Product of the Last K Numbers	C++ Python	ctor: O(1) add: O(1) get: O(1)	O(n)	Medium
1357	Apply Discount Every n Orders	C++ Python	ctor: O(m) getBill: O(p)	O(m)	Medium
1381	Design a Stack With Increment Operation	C++ Python	ctor: O(1) push: O(1) pop: O(1) increment: O(1)	O(n)	Medium
1396	Design Underground System	C++ Python	ctor: O(1) checkin: O(1) checkout: O(1) getaverage: O(1)	O(n)	Medium
1429	First Unique Number	C++ Python	ctor: O(k) add: O(1) showFirstUnique: O(1)	O(n)	Medium	🔒	LinkedHashSet
1472	Design Browser History	C++ Python	ctor: O(1) visit: O(1) back: O(1) forward: O(1)	O(n)	Medium
1476	Subrectangle Queries	C++ Python	ctor: O(1) update: O(1) get: O(u)	O(u)	Medium
1483	Kth Ancestor of a Tree Node	C++ Python	ctor: O(n logh)* get: O(logh)	O(n logh)*	Hard		DP, Binary Lifting
1500	Design a File Sharing System	C++ Python	ctor: O(1) join: O(logu + c) leave: O(logu + c) request: O(u)	O(u c)*	Medium	🔒
1570	Dot Product of Two Sparse Vectors	C++ Python	ctor: O(n) dot_product: O(min(n, m))	O(n)	Medium	🔒
1586	Binary Search Tree Iterator II	C++ Python	O(1), amortized	O(h)	Medium	🔒
1600	Throne Inheritance	C++ Python	ctor: O(1) birth: O(1) death: O(1) inherit: O(n)	O(n)	Medium
1603	Design Parking System	C++ Python	O(1)	O(1)	Easy
1622	Fancy Sequence	C++ Python	O(1)	O(n)	Hard		`Euler's Theorem`
1628	Design an Expression Tree With Evaluate Function	C++ Python	O(n)	O(h)	Medium	🔒
1656	Design an Ordered Stream	C++ Python	O(1), amortized	O(n)	Easy
1670	Design Front Middle Back Queue	C++ Python	O(1)	O(n)	Medium
1756	Design Most Recently Used Queue	C++ Python	ctor: O(nlogn) fetch: O(logn)	O(n)	Medium	🔒	Sorted List, BIT, Fenwick Tree, Square Root Decomposition
1797	Design Authentication Manager	C++ Python	ctor: O(1) generate: O(1), amortized renew: O(1), amortized count: O(1), amortized	O(n)	Medium		OrderedDict
1804	Implement Trie II (Prefix Tree)	C++ Python	ctor: O(1) insert: O(n) count_word: O(n) count_prefix: O(n) erase: O(n)	O(t)	Medium	🔒	Trie
1825	Finding MK Average	C++ Python	ctor: O(1) add_element: O(logn) calc_mkaverge: O(1)	O(m)	Hard		Sorted List
1845	Seat Reservation Manager	C++ Python	ctor: O(n) reserve: O(logn) unreserve: O(logn)	O(n)	Medium		Heap
1865	Finding Pairs With a Certain Sum	C++ Python	ctor: O(n1 + n2) add: O(1) count: O(n1)	O(n1 + n2)	Medium		Hash Table
1912	Design Movie Rental System	C++ Python	ctor: O(nlogn) search: O(logn) rent: O(logn) drop: O(logn) report: O(logn)	O(n)	Hard		Ordered List
1993	Operations on Tree	C++ Python	ctor: O(n) lock: O(1) unlock: O(1) upgrade: O(n)	O(n)	Medium
2013	Detect Squares	C++ Python	ctor: O(1) add: O(1) count: O(n)	O(n)	Medium
2034	Stock Price Fluctuation	C++ Python	ctor: O(1) update: O(logn) current: O(1) max: O(1) min: O(1)	O(n)	Medium		Sorted List, Heap
2043	Simple Bank System	C++ Python	ctor: O(1) transer: O(1) deposit: O(1) withdraw: O(1)	O(1)	Medium
2069	Walking Robot Simulation II	C++ Python	O(1)	O(1)	Medium		Simulation, Math
2080	Range Frequency Queries	C++ Python	ctor: O(n) query: O(logn)	O(n)	Medium		Binary Search
2102	Sequentially Ordinal Rank Tracker	C++ Python	add: O(logn) get: O(logn)	O(n)	Hard		Sorted List
2166	Design Bitset	C++ Python	ctor: O(n) fix: O(1) fix: O(1) unfix: O(1) flip: O(1) all: O(1) one: O(1) count: O(1) toString: O(n)	O(n)	Medium
2227	Encrypt and Decrypt Strings	C++ Python	ctor: O(m + d) encrypt: O(n) decrypt: O(n)	O(n)	Hard		Freq Table
2241	Design an ATM Machine	C++ Python	ctor: O(1) deposit: O(1) withdraw: O(1)	O(1)	Medium		Greedy
2254	Design Video Sharing Platform	C++ Python	ctor: O(1) upload: O(logn + l) remove: O(logn) like: O(1) dislike: O(1) view: O(1) getLikesAndDislikes: O(1) getViews: O(1)	O(n l)*	Hard	🔒	Heap
2276	Count Integers in Intervals	C++ Python	ctor: O(1) add: O(logn), amortized Count: O(1)	O(n)	Hard		Sorted List

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Concurrency

#	Title	Solution	Time	Space	Difficulty	Tag
1114	Print in Order	C++ Python	O(n)	O(1)	Easy
1115	Print FooBar Alternately	C++ Python	O(n)	O(1)	Medium
1116	Print Zero Even Odd	C++ Python	O(n)	O(1)	Medium
1117	Building H2O	C++ Python	O(n)	O(1)	Hard
1188	Design Bounded Blocking Queue	C++ Python	O(n)	O(1)	Medium	🔒
1195	Fizz Buzz Multithreaded	C++ Python	O(n)	O(1)	Medium
1226	The Dining Philosophers	C++ Python	O(n)	O(1)	Medium
1242	Web Crawler Multithreaded	C++ Python	O(\|V\| + \|E\|)	O(\|V\|)	Medium	🔒
1279	Traffic Light Controlled Intersection	C++ Python	O(n)	O(1)	Easy	🔒

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SQL

#	Title	Solution	Time	Space	Difficulty	Tag	Note
1045	Customers Who Bought All Products	MySQL	O(n + k)	O(n + k)	Medium	🔒
1050	Actors and Directors Who Cooperated At Least Three Times	MySQL	O(n)	O(n)	Easy	🔒
1068	Product Sales Analysis I	MySQL	O(m + n)	O(m + n)	Easy	🔒
1069	Product Sales Analysis II	MySQL	O(n)	O(n)	Easy	🔒
1070	Product Sales Analysis III	MySQL	O(n)	O(n)	Medium	🔒
1075	Project Employees I	MySQL	O(m + n)	O(m + n)	Easy	🔒
1076	Project Employees II	MySQL	O(n)	O(n)	Easy	🔒
1077	Project Employees III	MySQL	O((m + n)^2)	O(m + n)	Medium	🔒
1082	Sales Analysis I	MySQL	O(n)	O(n)	Easy	🔒
1083	Sales Analysis II	MySQL	O(m + n)	O(m + n)	Easy	🔒
1084	Sales Analysis III	MySQL	O(m + n)	O(m + n)	Easy	🔒
1097	Game Play Analysis V	MySQL	O(n^2)	O(n)	Hard	🔒
1098	Unpopular Books	MySQL	O(m + n)	O(n)	Medium	🔒
1107	New Users Daily Count	MySQL	O(n)	O(n)	Medium	🔒
1112	Highest Grade For Each Student	MySQL	O(nlogn)	O(n)	Medium	🔒
1113	Reported Posts	MySQL	O(n)	O(n)	Easy	🔒
1126	Active Businesses	MySQL	O(n)	O(n)	Medium	🔒
1127	User Purchase Platform	MySQL	O(n)	O(n)	Hard	🔒
1132	Reported Posts II	MySQL	O(m + n)	O(n)	Medium	🔒
1141	User Activity for the Past 30 Days I	MySQL	O(n)	O(n)	Easy	🔒
1142	User Activity for the Past 30 Days II	MySQL	O(n)	O(n)	Easy	🔒
1148	Article Views I	MySQL	O(nlogn)	O(n)	Easy	🔒
1149	Article Views II	MySQL	O(nlogn)	O(n)	Medium	🔒
1158	Market Analysis I	MySQL	O(m + n)	O(m + n)	Medium	🔒
1159	Market Analysis II	MySQL	O(m + n)	O(m + n)	Hard	🔒
1164	Product Price at a Given Date	MySQL	O(mlogn)	O(m)	Medium	🔒
1173	Immediate Food Delivery I	MySQL	O(n)	O(1)	Easy	🔒
1174	Immediate Food Delivery II	MySQL	O(n)	O(m)	Medium	🔒
1179	Reformat Department Table	MySQL	O(n)	O(n)	Easy	🔒
1193	Monthly Transactions I	MySQL	O(n)	O(n)	Medium	🔒
1194	Tournament Winners	MySQL	O(m + n + nlogn)	O(m + n)	Hard	🔒
1204	Last Person to Fit in the Elevator	MySQL	O(nlogn)	O(n)	Medium	🔒
1205	Monthly Transactions II	MySQL	O(n)	O(n)	Medium	🔒
1211	Queries Quality and Percentage	MySQL	O(n)	O(n)	Easy
1212	Team Scores in Football Tournament	MySQL	O(nlogn)	O(n)	Medium
1225	Report Contiguous Dates	MySQL	O(nlogn)	O(n)	Hard	🔒
1241	Number of Comments per Post	MySQL	O(n)	O(n)	Easy	🔒
1251	Average Selling Price	MySQL	O(n)	O(n)	Easy	🔒
1264	Page Recommendations	MySQL	O(m + n)	O(m)	Medium	🔒
1270	All People Report to the Given Manager	MySQL	O(n)	O(n)	Medium	🔒
1280	Students and Examinations	MySQL	O((m n) * log(m * n))*	O(m n)*	Easy	🔒
1285	Find the Start and End Number of Continuous Ranges	MySQL	O(n)	O(n)	Medium	🔒
1294	Weather Type in Each Country	MySQL	O(m + n)	O(n)	Easy	🔒
1303	Find the Team Size	MySQL	O(n)	O(n)	Easy	🔒
1308	Running Total for Different Genders	MySQL	O(nlogn)	O(n)	Medium	🔒
1321	Restaurant Growth	MySQL	O(nlogn)	O(n)	Medium	🔒
1322	Ads Performance	MySQL	O(nlogn)	O(n)	Easy	🔒
1327	List the Products Ordered in a Period	MySQL	O(n)	O(n)	Easy	🔒
1336	Number of Transactions per Visit	MySQL	O(m + n)	O(m + n)	Medium	🔒
1341	Movie Rating	MySQL	O(nlogn)	O(n)	Medium	🔒
1350	Students With Invalid Departments	MySQL	O(n)	O(n)	Easy	🔒
1355	Activity Participants	MySQL	O(n)	O(n)	Medium	🔒
1364	Number of Trusted Contacts of a Customer	MySQL	O(n + m + l + nlogn)	O(n + m + l)	Medium	🔒
1369	Get the Second Most Recent Activity	MySQL	O(nlogn)	O(n)	Hard	🔒
1378	Replace Employee ID With The Unique Identifier	MySQL	O(n)	O(n)	Easy	🔒
1384	Total Sales Amount by Year	MySQL	O(nlogn)	O(n)	Hard	🔒
1393	Capital Gain/Loss	MySQL	O(n)	O(n)	Medium	🔒
1398	Customers Who Bought Products A and B but Not C	MySQL	O(m + n)	O(m + n)	Medium	🔒
1407	Top Travellers	MySQL	O(m + nlogn)	O(m + n)	Easy	🔒
1412	Find the Quiet Students in All Exams	MySQL	O(m + nlogn)	O(m + n)	Hard	🔒
1421	NPV Queries	MySQL	O(n)	O(n)	Medium	🔒
1435	Create a Session Bar Chart	MySQL	O(n)	O(1)	Easy	🔒
1440	Evaluate Boolean Expression	MySQL	O(n)	O(n)	Medium	🔒
1445	Apples & Oranges	MySQL	O(n)	O(n)	Medium	🔒
1454	Active Users	MySQL	O(nlogn)	O(n)	Medium	🔒
1459	Rectangles Area	MySQL	O(n^2)	O(n^2)	Medium	🔒
1468	Calculate Salaries	MySQL	O(m + n)	O(m + n)	Easy	🔒
1479	Sales by Day of the Week	MySQL	O(m + n)	O(n)	Hard	🔒
1484	Group Sold Products By The Date	MySQL	O(nlogn)	O(n)	Easy	🔒
1495	Friendly Movies Streamed Last Month	MySQL	O(n)	O(n)	Easy	🔒
1501	Countries You Can Safely Invest In	MySQL	O(n)	O(n)	Medium	🔒
1511	Customer Order Frequency	MySQL	O(n)	O(n)	Easy	🔒
1517	Find Users With Valid E-Mails	MySQL	O(n)	O(n)	Easy	🔒	Regex
1527	Patients With a Condition	MySQL	O(n)	O(n)	Easy	🔒	Regex
1532	The Most Recent Three Orders	MySQL	O(nlogn)	O(n)	Medium	🔒
1543	Fix Product Name Format	MySQL	O(nlogn)	O(n)	Easy	🔒
1549	The Most Recent Orders for Each Product	MySQL	O(nlogn)	O(n)	Medium	🔒
1555	Bank Account Summary	MySQL	O(m + n)	O(m + n)	Medium	🔒
1565	Unique Orders and Customers Per Month	MySQL	O(n)	O(n)	Easy	🔒
1571	Warehouse Manager	MySQL	O(n)	O(n)	Medium	🔒
1581	Customer Who Visited but Did Not Make Any Transactions	MySQL	O(n)	O(n)	Easy	🔒
1587	Bank Account Summary II	MySQL	O(m + n)	O(m + n)	Easy	🔒
1596	The Most Frequently Ordered Products for Each Customer	MySQL	O(n)	O(n)	Medium	🔒
1607	Sellers With No Sales	MySQL	O(nlogm)	O(n + m)	Medium	🔒
1613	Find the Missing IDs	MySQL	O(n^2)	O(n)	Medium	🔒
1623	All Valid Triplets That Can Represent a Country	MySQL	O(n^3)	O(n^3)	Easy	🔒
1633	Percentage of Users Attended a Contest	MySQL	O(m + nlogn)	O(n)	Easy	🔒
1635	Hopper Company Queries I	MySQL	O(d + r + tlogt)	O(d + r + t)	Hard	🔒
1645	Hopper Company Queries II	MySQL	O(d + r + tlogt)	O(d + r + t)	Hard	🔒
1651	Hopper Company Queries III	MySQL	O(d + r + tlogt)	O(d + r + t)	Hard	🔒
1661	Average Time of Process per Machine	MySQL	O(n)	O(n)	Easy	🔒
1667	Fix Names in a Table	MySQL	O(nlogn)	O(n)	Easy	🔒
1677	Product's Worth Over Invoices	MySQL	O(nlogn)	O(n)	Easy	🔒
1683	Invalid Tweets	MySQL	O(n)	O(n)	Easy	🔒
1693	Daily Leads and Partners	MySQL	O(n)	O(n)	Easy	🔒
1699	Number of Calls Between Two Persons	MySQL	O(n)	O(n)	Medium	🔒
1709	Biggest Window Between Visits	MySQL	O(nlogn)	O(n)	Medium	🔒
1715	Count Apples and Oranges	MySQL	O(n)	O(n)	Medium	🔒
1729	Find Followers Count	MySQL	O(nlogn)	O(n)	Easy	🔒
1731	The Number of Employees Which Report to Each Employee	MySQL	O(nlogn)	O(n)	Easy	🔒
1741	Find Total Time Spent by Each Employee	MySQL	O(nlogn)	O(n)	Easy	🔒
1747	Leetflex Banned Accounts	MySQL	O(n^2)	O(n)	Medium	🔒
1757	Recyclable and Low Fat Products	MySQL	O(n)	O(n)	Easy	🔒
1767	Find the Subtasks That Did Not Execute	MySQL	O(n c)*	O(n c)*	Hard	🔒
1777	Product's Price for Each Store	MySQL	O(n)	O(n)	Easy	🔒
1783	Grand Slam Titles	MySQL	O(n)	O(n)	Medium	🔒
1789	Primary Department for Each Employee	MySQL	O(n)	O(n)	Easy	🔒
1795	Rearrange Products Table	MySQL	O(n)	O(n)	Easy	🔒
1809	Ad-Free Sessions	MySQL	O(n)	O(n)	Easy	🔒
1811	Find Interview Candidates	MySQL	O(nlogn)	O(n)	Medium	🔒
1821	Find Customers With Positive Revenue this Year	MySQL	O(n)	O(n)	Easy	🔒
1831	Maximum Transaction Each Day	MySQL	O(nlogn)	O(n)	Medium	🔒
1841	League Statistics	MySQL	O(nlogn)	O(n)	Medium	🔒
1843	Suspicious Bank Accounts	MySQL	O(nlogn)	O(n)	Medium	🔒
1853	Convert Date Format	MySQL	O(n)	O(n)	Easy	🔒
1867	Orders With Maximum Quantity Above Average	MySQL	O(n)	O(n)	Easy	🔒
1873	Calculate Special Bonus	MySQL	O(n)	O(n)	Easy	🔒
1875	Group Employees of the Same Salary	MySQL	O(nlogn)	O(n)	Medium	🔒
1890	The Latest Login in 2020	MySQL	O(n)	O(n)	Easy	🔒
1892	Page Recommendations II	MySQL	O(n m)*	O(n m)*	Hard	🔒
1907	Count Salary Categories	MySQL	O(n)	O(n)	Medium	🔒
1917	Leetcodify Friends Recommendations	MySQL	O(n^2)	O(n^2)	Hard	🔒
1919	Leetcodify Similar Friends	MySQL	O(n l)*	O(n l)*	Hard	🔒
1934	Confirmation Rate	MySQL	O(n + m)	O(n + m)	Medium	🔒
1939	Users That Actively Request Confirmation Messages	MySQL	O(nlogn)	O(n)	Easy	🔒
1949	Strong Friendship	MySQL	O(n^3)	O(n^2)	Medium	🔒
1951	All the Pairs With the Maximum Number of Common Followers	MySQL	O(n^3)	O(n^2)	Medium	🔒
1965	Employees With Missing Information	MySQL	O(nlogn)	O(n)	Easy	🔒
1972	First and Last Call On the Same Day	MySQL	O(n)	O(n)	Hard	🔒
1978	Employees Whose Manager Left the Company	MySQL	O(nlogn)	O(n)	Easy	🔒
1988	Find Cutoff Score for Each School	MySQL	O(n m)*	O(n m)*	Medium	🔒
1990	Count the Number of Experiments	MySQL	O(n)	O(n)	Easy	🔒
2004	The Number of Seniors and Juniors to Join the Company	MySQL	O(nlogn)	O(n)	Hard	🔒
2010	The Number of Seniors and Juniors to Join the Company II	MySQL	O(nlogn)	O(n)	Hard	🔒
2020	Number of Accounts That Did Not Stream	MySQL	O(m + n)	O(m + n)	Medium	🔒
2026	Low-Quality Problems	MySQL	O(nlogn)	O(n)	Easy	🔒
2041	Accepted Candidates From the Interviews	MySQL	O(m + n)	O(m + n)	Medium	🔒
2051	The Category of Each Member in the Store	MySQL	O(m + n)	O(m + n)	Medium	🔒
2066	Account Balance	MySQL	O(nlogn)	O(n)	Medium	🔒
2072	The Winner University	MySQL	O(n)	O(n)	Easy	🔒
2082	The Number of Rich Customers	MySQL	O(n)	O(n)	Easy	🔒
2084	Drop Type 1 Orders for Customers With Type 0 Orders	MySQL	O(nlogn)	O(n)	Medium	🔒
2112	The Airport With the Most Traffic	MySQL	O(n)	O(n)	Medium	🔒
2118	Build the Equation	MySQL	O(nlogn)	O(n)	Hard	🔒
2142	The Number of Passengers in Each Bus I	MySQL	O(p b + blogb)*	O(p b)*	Medium	🔒
2153	The Number of Passengers in Each Bus II	MySQL	O(p b + blogb)*	O(p b)*	Hard	🔒
2159	Order Two Columns Independently	MySQL	O(nlogn)	O(n)	Medium	🔒
2173	Longest Winning Streak	MySQL	O(nlogn)	O(n)	Hard	🔒
2175	The Change in Global Rankings	MySQL	O(nlogn)	O(n)	Medium	🔒
2199	Finding the Topic of Each Post	MySQL	O(n mlogm)*	O(n m)*	Hard	🔒
2205	The Number of Users That Are Eligible for Discount	MySQL	O(n)	O(n)	Easy	🔒
2228	Users With Two Purchases Within Seven Days	MySQL	O(nlogn)	O(n)	Medium	🔒
2230	The Users That Are Eligible for Discount	MySQL	O(nlogn)	O(n)	Easy	🔒
2238	Number of Times a Driver Was a Passenger	MySQL	O(n)	O(n)	Medium	🔒
2252	Dynamic Pivoting of a Table	MySQL	O(n m)*	O(n m)*	Hard	🔒
2253	Dynamic Unpivoting of a Table	MySQL	O(n m)*	O(n m)*	Hard	🔒

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Shell Script

#	Title	Solution	Time	Space	Difficulty	Tag	Note

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License

Holychung/LeetCode-Solutions

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