Solved some of top 150 leetcode problems

Author: jyotisirswa

DataStrucutureQuestions/Array/121. Best Time to Buy and Sell Stock.playground/Contents.swift

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+import UIKit
+
+//https://leetcode.com/problems/best-time-to-buy-and-sell-stock/description/?envType=study-plan-v2&envId=top-interview-150
+//Time Complexity :- O(n), space complexity is O(1)
+public func maxProfit(_ prices: [Int]) -> Int {
+    var minPrice = Int.max
+    var maxProfit = 0
+    for price in prices {
+        minPrice = min(price, minPrice)
+        maxProfit = max(price - minPrice, maxProfit)
+    }
+    return maxProfit
+}
+
+print("Max profit of [7,1,5,3,6,4] is :- \(maxProfit([7,1,5,3,6,4]))") //Buy on second day & sell on 5th day
+print("Max profit of [7,6,4,3,1] is :- \(maxProfit([7,6,4,3,1]))") //in every sell it gonna be loss
+

DataStrucutureQuestions/Array/BuySellProblem.playground/contents.xcplayground renamed to DataStrucutureQuestions/Array/121. Best Time to Buy and Sell Stock.playground/contents.xcplayground

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+import UIKit
+
+//https://leetcode.com/problems/best-time-to-buy-and-sell-stock-ii/description/?envType=study-plan-v2&envId=top-interview-150
+//Time Complexity :- O(n), space complexity is O(1)
+
+func maxProfit(_ prices: [Int]) -> Int {
+    var profit = 0
+    for i in 1..<prices.count {
+        if prices[i] > prices[i - 1] {
+            profit +=  prices[i] - prices[i - 1]
+        }
+    }
+    return profit
+}
+print("Max profit of [7,1,5,3,6,4] is :- \(maxProfit([7,1,5,3,6,4]))") //Buy on second day & sell on 5th day
+//[1,2,3,4,5]
+print("Max profit of [1,2,3,4,5] is :- \(maxProfit([1,2,3,4,5]))") //Buy on second day & sell on 5th day
+

DataStrucutureQuestions/Array/122. Best Time to Buy and Sell Stock II.playground/Contents.swift

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+<?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/Array/122. Best Time to Buy and Sell Stock II.playground/contents.xcplayground

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+import UIKit
+
+//https://leetcode.com/problems/candy/description/?envType=study-plan-v2&envId=top-interview-150
+
+func candy(_ ratings: [Int]) -> Int {
+    var candiesArray = Array(repeating : 1, count : ratings.count)
+    for i in 1..<ratings.count where  ratings[i] > ratings[i - 1] {
+        candiesArray[i] = candiesArray[i - 1] + 1
+    }
+    for i in (0..<ratings.count - 1).reversed() where ratings[i] > ratings[i + 1] {
+        candiesArray[i] = max(candiesArray[i], candiesArray[i + 1] + 1)
+    }
+    return candiesArray.reduce(0, +)
+}
+
+print("minimum candies needed for array :- [1,0,2] is \(candy([1,0,2]))")
+print("minimum candies needed for array :- [5,4,3,5,6,2] is \(candy([5,4,3,5,6,2]))")

DataStrucutureQuestions/Array/135. Candy.playground/Contents.swift

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+<?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/Array/135. Candy.playground/contents.xcplayground

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+import UIKit
+
+//https://leetcode.com/problems/product-of-array-except-self/description/?envType=study-plan-v2&envId=top-interview-150
+//APPROACH 1 :- Complexity This approach has a time complexity of O(n)O(n)O(n) and a space complexity of O(n)O(n)O(n), where nnn is the length of the input array nums.
+func productExceptSelf(_ nums: [Int]) -> [Int] {
+    var prefix = Array(repeating: 1, count: nums.count)
+    var suffix = Array(repeating: 1, count: nums.count)
+    var result = Array(repeating: 0, count: nums.count)
+    for i in 1 ..< nums.count {
+        prefix[i] = prefix[i - 1] * nums[i - 1]
+    }
+    
+    for i in (0 ..< nums.count - 1).reversed() {
+        suffix[i] = suffix[i + 1] * nums[i + 1]
+    }
+    for i in 0 ..< result.count {
+        result[i] = prefix[i] * suffix[i]
+    }
+    
+    return result
+}
+print("Product of array elements except self using first approach is :- \(productExceptSelf([1,2,3,4]))")
+//APPROACH 2 :- Complexity This approach also has a time complexity of O(n)O(n)O(n) and a space complexity of O(1)O(1)O(1), where nnn is the length of the input array nums. (The output array does not count as extra space for space complexiy analysis)
+func productExceptSelfTwo(_ nums: [Int]) -> [Int] {
+    var result = Array(repeating: 1, count: nums.count)
+    
+    for i in 1 ..< nums.count {
+        result[i] = result[i - 1] * nums[i - 1]
+    }
+    
+    var suffix = 1
+    for i in (0 ..< nums.count).reversed() {
+        result[i] *= suffix
+        suffix *= nums[i]
+    }
+    
+    return result
+}
+print("Product of array elements except self using second approach is :- \(productExceptSelfTwo([1,2,3,4]))")
+

DataStrucutureQuestions/Array/238. Product of Array Except Self.playground/Contents.swift

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+<?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/Array/238. Product of Array Except Self.playground/contents.xcplayground

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+import UIKit
+
+//https://leetcode.com/problems/trapping-rain-water/description/?envType=study-plan-v2&envId=top-interview-150
+//APPROACH 1 :- TimeComplexity O(n), spaceComplexity O(n)
+func trap(_ height: [Int]) -> Int {
+    var maxLeftArray = Array(repeating:0, count : height.count)
+    var maxRightArray = Array(repeating:0, count : height.count)
+    var minLeftRightArray = Array(repeating:0, count : height.count)
+    var waterTrappedArray = Array(repeating:0, count : height.count)
+    
+    for i in 1..<height.count {
+        maxLeftArray[i] = max(height[i - 1], maxLeftArray[i - 1])
+    }
+    for i in (0..<height.count - 1).reversed() {
+        maxRightArray[i] = max(height[i + 1], maxRightArray[i + 1])
+    }
+    for i in 0..<height.count {
+        minLeftRightArray[i] = min(maxLeftArray[i], maxRightArray[i])
+    }
+    for i in 0..<height.count {
+        waterTrappedArray[i] =  minLeftRightArray[i] - height[i] > 0 ?  minLeftRightArray[i] - height[i] : 0
+    }
+    return waterTrappedArray.reduce(0, +)
+}
+print("Total water filled using approch 1 for elevation of [0,1,0,2,1,0,1,3,2,1,2,1] is : \(trap([0,1,0,2,1,0,1,3,2,1,2,1])) ")
+
+//APPROACH 2 :- TimeComplexity O(n), spaceComplexity O(1) using two pointer approach
+func trapApproachTwo(_ height: [Int]) -> Int {
+    var left = 0, right = height.count - 1, maxLeft = height[left], maxRight = height[right], waterFilled = 0
+    while left < right {
+        if maxLeft < maxRight {
+            left += 1
+            maxLeft = max(maxLeft, height[left])
+            waterFilled += maxLeft - height[left]
+        }
+        else {
+            right -= 1
+            maxRight = max(maxRight, height[right])
+            waterFilled += maxRight - height[right]
+        }
+    }
+    return waterFilled
+}
+print("Total water filled using approch 2 for elevation of [0,1,0,2,1,0,1,3,2,1,2,1] is : \(trapApproachTwo([0,1,0,2,1,0,1,3,2,1,2,1])) ")

DataStrucutureQuestions/Array/42. Trapping Rain Water.playground/Contents.swift

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+<?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/Array/42. Trapping Rain Water.playground/contents.xcplayground

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+import UIKit
+
+//https://leetcode.com/problems/jump-game-ii/description/?envType=study-plan-v2&envId=top-interview-150
+
+func jump(_ nums: [Int]) -> Int {
+    if nums.count <= 1 {
+        return 0
+    }
+    if nums[0] == 0 {
+        return -1
+    }
+    var valueMax = nums[0]
+    var steps = nums[0]
+    var jumps = 1
+    var i = 1
+    for i in 1..<nums.count {
+        if i == nums.count - 1 { return jumps }
+        valueMax = max(valueMax , i + nums[i])
+        steps -= 1
+        if (steps == 0) {
+            jumps +=  1
+            if i >= valueMax {
+            return -1
+        }
+         steps = valueMax - i
+        }
+    }
+    return -1
+}
+print("Minimum jumps required for array [2,3,1,1,4] is :- \(jump([2,3,1,1,4]))")

DataStrucutureQuestions/Array/45. Jump Game II.playground/Contents.swift

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+<?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/Array/45. Jump Game II.playground/contents.xcplayground

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+import UIKit
+
+//https://leetcode.com/problems/integer-to-roman/
+//TimeComplexity : O(n)
+
+func intToRoman(_ num: Int) -> String {
+   let arrayOfRomanKeys = [["M": 1000], ["CM": 900], ["D": 500], ["CD": 400],
+                            ["C": 100], ["XC": 90], ["L": 50], ["XL": 40], ["X": 10],
+                            ["IX": 9], ["V": 5], ["IV": 4], ["I": 1]]
+
+   var output = ""
+   var num = num
+   for (_, dictionary) in arrayOfRomanKeys.enumerated() {
+       output += String(repeating: dictionary.keys.first!, count: num / dictionary.values.first!)
+       if num / dictionary.values.first! != 0 {
+           num -= dictionary.values.first! * (num / dictionary.values.first!)
+       }
+   }
+
+   return output
+}
+print("Interger to Roman conversion of 3 = \(intToRoman(3))")
+print("Interger to Roman conversion of 58 = \(intToRoman(58))")
+print("Interger to Roman conversion of 1994 = \(intToRoman(1994))")
+

DataStrucutureQuestions/Array/BuySellProblem.playground/Contents.swift

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+<?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/Array/BuySellProblem.playground/timeline.xctimeline

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+import UIKit
+
+//https://leetcode.com/problems/roman-to-integer/description/?envType=study-plan-v2&envId=top-interview-150
+
+func romanToInt(_ s: String) -> Int {
+    var romanToInt : [Character : Int] = [ "I": 1,
+                                           "V": 5,
+                                           "X": 10,
+                                           "L": 50,
+                                           "C": 100,
+                                           "D": 500,
+                                           "M": 1000]
+    var integerNumber = 0
+    for i in 0..<s.count-1 {
+        let currentCharacter = s[s.index(s.startIndex, offsetBy: i)]
+        let nextCharacter = s[s.index(s.startIndex, offsetBy: i + 1)]
+        if romanToInt[currentCharacter]! >= romanToInt[nextCharacter]! {
+            integerNumber += romanToInt[currentCharacter]!
+        }
+        else {
+            integerNumber -= romanToInt[currentCharacter]!
+        }
+    }
+    integerNumber += romanToInt[s.last!]!
+    return integerNumber
+}
+print("Roman to integer conversion of III is :- \(romanToInt("III"))")
+print("Roman to integer conversion of LVIII is :- \(romanToInt("LVIII"))")
+print("Roman to integer conversion of MCMXCIV is :- \(romanToInt("MCMXCIV"))")

DataStrucutureQuestions/String/12. Integer to Roman.playground/Contents.swift

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+<?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/String/12. Integer to Roman.playground/contents.xcplayground

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+import UIKit
+
+//https://leetcode.com/problems/reverse-words-in-a-string/?envType=study-plan-v2&envId=top-interview-150
+// - Complexity:
+//   - time: O(n), where n is the number of words in the input string.
+//   - space: O(m), where m is the length of the input string.
+
+func reverseWords(_ s: String) -> String {
+  var arrayFromString = s.split(separator: " ")
+  var startIndex = 0
+  var endIndex = arrayFromString.count - 1
+  
+  while startIndex < endIndex {
+      arrayFromString.swapAt(startIndex, endIndex)
+      startIndex += 1
+      endIndex -= 1
+  }
+  return arrayFromString.joined(separator: " ")
+}
+print("Reverse of the sky is blue is : \(reverseWords("the sky is blue"))")

DataStrucutureQuestions/String/13. Roman to Integer.playground/Contents.swift

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+<?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/String/13. Roman to Integer.playground/contents.xcplayground

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+import UIKit
+
+//https://leetcode.com/problems/length-of-last-word/?envType=study-plan-v2&envId=top-interview-150
+//timeComplexity : O(n), spaceComplexity : O(1)
+
+func lengthOfLastWord(_ s: String) -> Int {
+    // var lastWord = s.trimmingCharacters(in: .whitespacesAndNewlines).components(separatedBy: " ")
+    // return lastWord.last?.count ?? 0
+    var countOfLastWord = 0
+    for character in s.reversed() {
+        if character != " " {
+            countOfLastWord += 1
+        } else if countOfLastWord > 0 {
+            return countOfLastWord
+        }
+    }
+    return countOfLastWord
+}
+
+print("Length of Last word of Hello World is :- \(lengthOfLastWord("Hello World"))")
+print("Length of Last word of    fly me   to   the moon   is :- \(lengthOfLastWord("   fly me   to   the moon  "))")
+

DataStrucutureQuestions/String/151. Reverse Words in a String.playground/Contents.swift

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+<?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>