leetcode problem solved related to stack, interval, pointers & hasmaps.

Author: jyotisirswa

DataStrucutureQuestions/HashMap/1. Two Sum.playground/Contents.swift

@@ -0,0 +1,19 @@
+import UIKit
+
+//https://leetcode.com/problems/two-sum/
+
+func twoSum(_ nums: [Int], _ target: Int) -> [Int] {
+    var hashMap = [Int : Int]()
+    
+    for (index, value) in nums.enumerated() {
+        if hashMap[value] != nil {
+            return [hashMap[value]!, index]
+        } else {
+            hashMap[target - value] = index
+        }
+    }
+    return []
+}
+
+print(twoSum([2,7,11,15], 9))
+print(twoSum([3,2,4], 6))

DataStrucutureQuestions/HashMap/1. Two Sum.playground/contents.xcplayground

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

DataStrucutureQuestions/HashMap/128. Longest Consecutive Sequence.playground/Contents.swift

@@ -0,0 +1,22 @@
+import UIKit
+
+//https://leetcode.com/problems/longest-consecutive-sequence/
+
+func longestConsecutive(_ nums: [Int]) -> Int {
+    var numSet = Set(nums)
+    var longest = 0
+    
+    for num in nums {
+        if !numSet.contains(num - 1) {
+            var length = 0
+            while numSet.contains(num + length) {
+                length += 1
+                longest = max(longest, length)
+            }
+        }
+    }
+    
+    return longest
+}
+
+print(longestConsecutive([100,4,200,1,3,2]))

DataStrucutureQuestions/HashMap/128. Longest Consecutive Sequence.playground/contents.xcplayground

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

DataStrucutureQuestions/HashMap/166. Fraction to Recurring Decimal.playground/Contents.swift

@@ -2,8 +2,6 @@ import UIKit
 
 //https://leetcode.com/problems/fraction-to-recurring-decimal/
 
-
-
 func fractionToDecimal(_ numerator: Int, _ denominator: Int) -> String {
     var result = ""
     var remainderMap : [Int : Int] = [:]

DataStrucutureQuestions/HashMap/202. Happy Number.playground/Contents.swift

@@ -0,0 +1,32 @@
+import UIKit
+
+//https://leetcode.com/problems/happy-number/
+
+func isHappy(_ n: Int) -> Bool {
+    var slow = n
+    var fast = n
+    
+    while true {
+        slow = getNext(slow)
+        fast = getNext(fast)
+        fast = getNext(fast)
+        if slow == fast {
+            break
+        }
+    }
+    return fast == 1
+}
+
+private func getNext(_ n: Int) -> Int {
+    var sum = 0
+    var input = n
+        
+    while input > 0 {
+        let remainder = input % 10
+        sum += remainder * remainder
+        input /= 10
+    }
+    
+    return sum
+}
+print(isHappy(19))

DataStrucutureQuestions/HashMap/202. Happy Number.playground/contents.xcplayground

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

DataStrucutureQuestions/HashMap/205. Isomorphic Strings.playground/Contents.swift

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

DataStrucutureQuestions/HashMap/205. Isomorphic Strings.playground/contents.xcplayground

@@ -0,0 +1,17 @@
+import UIKit
+
+//https://leetcode.com/problems/contains-duplicate-ii/
+
+func containsNearbyDuplicate(_ nums: [Int], _ k: Int) -> Bool {
+    var dict = [Int : Int]()
+    for (index, value) in nums.enumerated() {
+        if let duplicateIndex = dict[value], index - duplicateIndex <= k {
+            return true
+        }
+        dict[value] = index
+    }
+    return false
+}
+
+print(containsNearbyDuplicate([1,2,3,1], 3))
+print(containsNearbyDuplicate([1,2,3,1,2,3], 2))

DataStrucutureQuestions/HashMap/219. Contains Duplicate II.playground/Contents.swift

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

DataStrucutureQuestions/HashMap/219. Contains Duplicate II.playground/contents.xcplayground

@@ -0,0 +1,26 @@
+import UIKit
+
+//https://leetcode.com/problems/valid-anagram/
+
+func isAnagram(_ s: String, _ t: String) -> Bool {
+    var sCountHashMap = [Character: Int]()
+    var tCountHashMap = [Character: Int]()
+    
+    if s.count != t.count {
+        return false
+    }
+    
+    for index in s.indices {
+        sCountHashMap[s[index]] = 1 + sCountHashMap[s[index], default: 0]
+        tCountHashMap[t[index]] = 1 + tCountHashMap[t[index], default: 0]
+    }
+    
+    for key in sCountHashMap.keys {
+        if sCountHashMap[key] != tCountHashMap[key] {
+            return false
+        }
+    }
+    return true
+}
+print(isAnagram("anagram", "nagaram"))
+print(isAnagram("rat", "car"))

DataStrucutureQuestions/HashMap/242. Valid Anagram.playground/Contents.swift

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

DataStrucutureQuestions/HashMap/242. Valid Anagram.playground/contents.xcplayground

@@ -0,0 +1,25 @@
+import UIKit
+
+//https://leetcode.com/problems/word-pattern/
+
+func wordPattern(_ pattern: String, _ s: String) -> Bool {
+    var hashMap = [Character : String.SubSequence]()
+    var patternArray = Array(pattern)
+    var sArray = s.split(separator: " ")
+    if patternArray.count != sArray.count {
+        return false
+    }
+    for i in 0..<sArray.count {
+        if hashMap[patternArray[i]] == nil {
+            hashMap[patternArray[i]] = sArray[i]
+        } else if hashMap[patternArray[i]] != sArray[i] {
+            return false
+        }
+    }
+    return hashMap.keys.count == Set(hashMap.values).count
+}
+
+print(wordPattern("abba", "dog cat cat dog"))
+print(wordPattern("abba", "dog cat cat fish"))
+print(wordPattern("aaaa", "dog cat cat dog"))
+

DataStrucutureQuestions/HashMap/290. Word Pattern.playground/Contents.swift

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

DataStrucutureQuestions/HashMap/290. Word Pattern.playground/contents.xcplayground

@@ -0,0 +1,26 @@
+import UIKit
+
+//https://leetcode.com/problems/ransom-note/description/
+
+func canConstruct(_ ransomNote: String, _ magazine: String) -> Bool {
+    var hashMap = [Character : Int]()
+    for character in magazine {
+        if hashMap[character] == nil {
+            hashMap[character] = 1
+        } else {
+            hashMap[character]! += 1
+        }
+    }
+    
+    for character in ransomNote {
+        if let count = hashMap[character], count > 0 {
+            hashMap[character]! -= 1
+        } else {
+            return false
+        }
+    }
+    return true
+}
+print(canConstruct("a", "b"))
+print(canConstruct("aa", "ab"))
+print(canConstruct("aa", "aab"))

DataStrucutureQuestions/HashMap/383. Ransom Note.playground/Contents.swift

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

DataStrucutureQuestions/HashMap/383. Ransom Note.playground/contents.xcplayground

@@ -0,0 +1,25 @@
+import UIKit
+
+//https://leetcode.com/problems/longest-palindrome/description/
+
+func longestPalindrome(_ s: String) -> Int {
+    var hashMap = [Character : Int]()
+    var palindromCount = 0
+    for character in s {
+        if hashMap[character] == nil {
+            hashMap[character] = 1
+        } else {
+            hashMap[character]! += 1
+        }
+    }
+    for (_, element) in hashMap {
+        if element % 2 == 0 {
+           palindromCount += element
+        } else {
+            palindromCount += element - 1
+        }
+    }
+    return palindromCount < s.count ? palindromCount + 1 : palindromCount
+}
+
+print(longestPalindrome("abccccdddeeeeeeff"))

DataStrucutureQuestions/HashMap/409. Longest Palindrome.playground/Contents.swift

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

DataStrucutureQuestions/HashMap/409. Longest Palindrome.playground/contents.xcplayground

@@ -0,0 +1,20 @@
+import UIKit
+
+//https://leetcode.com/problems/group-anagrams/
+
+func groupAnagrams(_ strs: [String]) -> [[String]] {
+    var result = [String: [String]]()
+    
+    for string in strs {
+        var countArray = [Int](repeating: 0, count: 26)
+        
+        for character in string {
+            countArray[Int(character.asciiValue! - Character("a").asciiValue!)] += 1
+        }
+        let key = countArray.map { String($0) }.joined(separator: ",")
+        result[key, default: []].append(string)
+    }
+    return Array(result.values)
+}
+
+print(groupAnagrams(["eat","tea","tan","ate","nat","bat"]))

DataStrucutureQuestions/HashMap/49. Group Anagrams.playground/Contents.swift

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

DataStrucutureQuestions/HashMap/49. Group Anagrams.playground/contents.xcplayground

@@ -0,0 +1,28 @@
+import UIKit
+
+//https://leetcode.com/problems/next-greater-element-i/description/
+
+func nextGreaterElement(_ nums1: [Int], _ nums2: [Int]) -> [Int] {
+    var stacks : [Int] = []
+    var mapping = [Int : Int]()
+    
+    for (_, value) in nums2.enumerated() {
+        while !stacks.isEmpty && value > stacks.last ?? 0 {
+            mapping[stacks.removeLast()] = value
+        }
+        stacks.append(value)
+    }
+    
+    while !stacks.isEmpty {
+        mapping[stacks.removeLast()] = -1
+    }
+    
+    var answer = [Int]()
+    
+    for num in nums1 {
+        answer.append(mapping[num]!)
+    }
+    return answer
+}
+
+print(nextGreaterElement([4,1,2], [1,3,4,2]))

DataStrucutureQuestions/HashMap/496. Next Greater Element I.playground/Contents.swift

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

DataStrucutureQuestions/HashMap/496. Next Greater Element I.playground/contents.xcplayground

@@ -0,0 +1,28 @@
+import UIKit
+
+//https://leetcode.com/problems/summary-ranges/
+
+func summaryRanges(_ nums: [Int]) -> [String] {
+var start = 0
+var end = 0
+var outPutAray = [String]()
+if nums.count == 1 {
+    return ["\(nums[start])"]
+}
+while end < nums.count - 1 {
+    if  nums[end + 1] - nums[end] == 1 {
+        end += 1
+    } else {
+        outPutAray.append(start != end ? "\(nums[start])->\(nums[end])" : "\(nums[end])")
+        end += 1
+        start = end
+    }
+    if nums[end] == nums.last {
+        outPutAray.append(start != end ? "\(nums[start])->\(nums[end])" : "\(nums[end])")
+    }
+}
+return outPutAray
+}
+
+print(summaryRanges([0,2,3,4,6,8,9]))
+

DataStrucutureQuestions/Intervals/228. Summary Ranges.playground/Contents.swift

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

DataStrucutureQuestions/Intervals/228. Summary Ranges.playground/contents.xcplayground

@@ -0,0 +1,22 @@
+import UIKit
+
+//https://leetcode.com/problems/minimum-number-of-arrows-to-burst-balloons/
+
+func findMinArrowShots(_ points: [[Int]]) -> Int {
+    var pointsSorted = points.sorted(by: { $0[1] < $1[1] })
+    var end = pointsSorted[0][1]
+    var arrows = 1
+
+    
+    for point in pointsSorted {
+        if point[0] > end {
+            arrows += 1
+            end = point[1]
+        }
+    }
+    
+    return arrows
+}
+
+
+print(findMinArrowShots([[10,16],[2,8],[1,6],[7,12]]))

DataStrucutureQuestions/Intervals/452. Minimum Number of Arrows to Burst Balloons.playground/Contents.swift

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>