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Author: partho-maple

leetcode.com/swift/DS_ALGO_PRAC.playground/Sources/swift/199_Binary_Tree_Right_Side_View.swift

@@ -14,6 +14,8 @@ import Foundation
  *     }
  * }
  */
+
+// DFS
 class Solution {
     func rightSideView(_ root: TreeNode?) -> [Int] {
         guard var root = root else {
@@ -37,3 +39,31 @@ class Solution {
         rightSideViewDFSHelper(root.left, currentDepth + 1, &maxDepthSoFar, &rightView)
     }
 }
+
+
+// BFS with level size measurement
+class Solution {
+    func rightSideView(_ root: TreeNode?) -> [Int] {
+        guard let root = root else {
+            return []
+        }
+        var result = [Int](), queue = [TreeNode](), currentLevelLength = 1
+        queue.append(root)
+        while !queue.isEmpty {
+            var rightMostNode = Int.min, currentLevelLength = queue.count
+            while currentLevelLength > 0 {
+                let node = queue.removeFirst()
+                rightMostNode = node.val
+                currentLevelLength -= 1
+                if let left = node.left {
+                    queue.append(left)
+                }
+                if let right = node.right {
+                    queue.append(right)
+                }
+            }
+            result.append(rightMostNode)
+        }
+        return result
+    }
+}

leetcode.com/swift/DS_ALGO_PRAC.playground/Sources/swift/31_Next_Permutation.swift

@@ -1,15 +1,14 @@
-
 import Foundation
 
+// My first attempt
 class Solution {
     func nextPermutation(_ nums: inout [Int]) {
         guard nums.count >= 2 else {
             return
         }
 
         for leftIdx in stride(from:(nums.count - 2), through:0, by:-1) {
-            var leftNum = nums[leftIdx]
-            var rightNum = nums[leftIdx + 1]
+            let leftNum = nums[leftIdx], rightNum = nums[leftIdx + 1]
             if leftNum < rightNum {
                 var swapIdx = leftIdx + 1
                 for i in (swapIdx..<nums.count) {
@@ -25,3 +24,29 @@ class Solution {
         nums.reverse()
     }
 }
+
+
+// My second attempt
+class Solution {
+    func nextPermutation(_ nums: inout [Int]) {
+        guard nums.count > 1 else {
+            return
+        }
+        for rightIdx in stride(from: nums.count - 1, through: 1, by: -1) {
+            let rightNum = nums[rightIdx], leftNum = nums[rightIdx - 1]
+            if rightNum > leftNum {
+                var swapIdx = rightIdx, nextGraterNum = rightNum
+                for j in swapIdx..<nums.count {
+                    if leftNum < nums[j] && nums[j] < nextGraterNum  {
+                        swapIdx = j
+                        nextGraterNum = nums[j]
+                    }
+                }
+                nums.swapAt(rightIdx - 1, swapIdx)
+                nums[rightIdx..<nums.count].sort()
+                return
+            }
+        }
+        nums.sort()
+    }
+}

leetcode.com/swift/DS_ALGO_PRAC.playground/Sources/swift/50_Pow(x, n).swift

@@ -0,0 +1,19 @@
+import Foundation
+
+// Video: https://www.youtube.com/watch?v=g9YQyYi4IQQ
+class Solution {
+    func myPow(_ x: Double, _ n: Int) -> Double {
+        if n == 0 {
+            return 1
+        }
+        if n < 0 {
+            return 1 / myPow(x, -n)
+        }
+        let half = myPow(x, n/2)
+        if n % 2 == 0 {
+            return half * half
+        } else {
+            return x * half * half
+        }
+    }
+}