Added new accepted solutions

Author: Michael Ho

Easy/0066-PlusOne.playground/Contents.swift

@@ -0,0 +1,28 @@
+// LeetCode: https://leetcode.com/problems/plus-one/description/
+// Difficulty: Easy
+
+class Solution {
+    func plusOne(_ digits: [Int]) -> [Int] {
+        var output: [Int] = digits
+        var index = digits.count - 1
+        output[index] += 1 // Add one
+        var addOne: Bool = output[index] >= 10
+        while index >= 0 {
+            output[index] += addOne ? 1 : 0
+            addOne = output[index] >= 10
+            output[index] = output[index] >= 10 ? 0 : output[index]
+            index -= 1
+        }
+        if addOne {
+            output.insert(1, at: 0)
+        }
+        return output
+    }
+}
+
+let solution = Solution()
+print("\(solution.plusOne([1,2,3]))") // [1,2,4]
+print("\(solution.plusOne([4,3,2,2]))") // [4,3,2,3]
+print("\(solution.plusOne([4,5,9,9]))") // [4,6,0,0]
+print("\(solution.plusOne([7,2,8,5,0,9,1,2,9,5,3,6,6,7,3,2,8,4,3,7,9,5,7,7,4,7,4,9,4,7,0,1,1,1,7,4,0,0,6]))") // Check runtime
+print("\(solution.plusOne([9]))") // [1,0]

0019-RemoveNthNodeFromEndofList.playground/contents.xcplayground renamed to Easy/0066-PlusOne.playground/contents.xcplayground

@@ -0,0 +1,43 @@
+// LeetCode: https://leetcode.com/problems/toeplitz-matrix/description/
+
+class Solution {
+    func isToeplitzMatrix(_ matrix: [[Int]]) -> Bool {
+        guard matrix.count > 0 else {
+            fatalError()
+        }
+        guard matrix.count > 1 else {
+            return true
+        }
+        var index = 0
+        var arrayIdx = 0
+        while arrayIdx < matrix.count {
+            while index < matrix[arrayIdx].count {
+                let num = matrix[arrayIdx][index]
+                var movingArrIdx = arrayIdx + 1
+                var movingIdx = index + 1
+                while movingArrIdx < matrix.count, movingIdx < matrix[movingArrIdx].count {
+                    guard matrix[movingArrIdx][movingIdx] == num else {
+                        return false
+                    }
+                    movingArrIdx += 1
+                    movingIdx += 1
+                }
+                index += 1
+            }
+            index = 0
+            arrayIdx += 1
+        }
+        return true
+    }
+}
+
+let solution = Solution()
+print("\(solution.isToeplitzMatrix([[1,2,3,4],[5,1,2,3],[9,5,1,2]]))") // True
+print("\(solution.isToeplitzMatrix([[1,2],[2,2]]))") // False
+print("\(solution.isToeplitzMatrix([[36,59,71,15,26,82,87],[56,36,59,71,15,26,82],[15,0,36,59,71,15,26]]))") // False
+/**
+ For the input above:
+ [36,59,71,15,26,82,87]
+ [56,36,59,71,15,26,82]
+ [15,0,36,59,71,15,26]
+ */

Easy/0766-ToeplitzMatrix.playground/Contents.swift

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

Easy/0766-ToeplitzMatrix.playground/contents.xcplayground

@@ -1,4 +1,4 @@
-// LeetCode: https://leetcode.com/problems/remove-nth-node-from-end-of-list/description/
+// LeetCode: https://leetcode.com/problems/swap-nodes-in-pairs/description/
 
 public class ListNode {
     public var val: Int
@@ -10,29 +10,32 @@ public class ListNode {
 }
 
 class Solution {
-    func removeNthFromEnd(_ head: ListNode?, _ n: Int) -> ListNode? {
+    func swapPairs(_ head: ListNode?) -> ListNode? {
         guard let head = head else {
             return nil
         }
-        var arr = convertToArray(head)
-        let index = arr.count - n - 1
-        guard index > 0 else {
-            return nil
+        // Handle edge case
+        guard let _ = head.next else {
+            return head
         }
-        arr[index].next = arr[index + 2]
-        return head
-    }
-    
-    private func convertToArray(_ head: ListNode) -> [ListNode] {
         var node: ListNode? = head
-        var arr: [ListNode] = []
-        while nil != node {
-            arr.append(node!)
-            node = node?.next
+        let newHead = node?.next
+        var prev: ListNode?
+        // Loop every two nodes
+        while let current = node, let next = node?.next {
+            // Change first node
+            current.next = next.next
+            // Move 2 indices
+            node = next.next
+            // Change second node
+            next.next = current
+            // Change the previous node of this pair
+            prev?.next = next
+            // Capture current node
+            prev = current
         }
-        return arr
+        return newHead
     }
-    
     func printLinkedList(_ head: ListNode) {
         var printedStr = ""
         var currentNode: ListNode? = head
@@ -54,5 +57,7 @@ let node3 = ListNode(3, node4)
 let node2 = ListNode(2, node3)
 let node1 = ListNode(1, node2)
 solution.printLinkedList(node1)
-solution.removeNthFromEnd(node1, 2)
-solution.printLinkedList(node1)
+
+// Reverse Linked List
+print("swap below:")
+solution.printLinkedList(solution.swapPairs(node1)!)

0019-RemoveNthNodeFromEndofList.playground/Contents.swift renamed to Medium/0024-SwapNodesInPairs.playground/Contents.swift

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

Medium/0024-SwapNodesInPairs.playground/contents.xcplayground

@@ -0,0 +1,27 @@
+// LeetCode: https://leetcode.com/problems/search-in-rotated-sorted-array/description/
+// Medium
+
+class Solution {
+    func search(_ nums: [Int], _ target: Int) -> Int {
+        return search(nums, target, 0)
+    }
+    func search(_ nums: [Int], _ target: Int, _ startIdx: Int) -> Int {
+        var output = -1
+        if nums.count == 1, nums.contains(target) {
+            return startIdx
+        }
+        let midIndex = nums.count / 2
+        let leftNums = Array(nums[0..<midIndex])
+        let rightNums = Array(nums[midIndex..<nums.count])
+        if leftNums.contains(target) {
+            output = search(leftNums, target, startIdx)
+        } else if rightNums.contains(target) {
+            output = search(rightNums, target, startIdx + midIndex)
+        }
+        return output
+    }
+}
+
+let solution = Solution()
+print("\(solution.search([4,5,6,7,0,1,2], 0))") // 4
+print("\(solution.search([4,5,6,7,0,1,2], 3))") // -1

Medium/0033-SearchInRotatedSortedArray.playground/Contents.swift

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

Medium/0033-SearchInRotatedSortedArray.playground/contents.xcplayground

@@ -0,0 +1,54 @@
+// LeetCode: https://leetcode.com/problems/rotate-image/description/
+// Reference: https://leetcode.com/problems/rotate-image/discuss/18872/A-common-method-to-rotate-the-image
+// Difficulty: Medium
+
+class Solution {
+    func rotate(_ matrix: inout [[Int]]) {
+        guard matrix.count > 1 else {
+            return
+        }
+        matrix.reverse()
+        var i = 0
+        var j = 0
+        while i < matrix.count {
+            j = i
+            while j < matrix[i].count {
+                (matrix[i][j], matrix[j][i]) = (matrix[j][i], matrix[i][j])
+                j += 1
+            }
+            i += 1
+        }
+    }
+}
+
+let solution = Solution()
+var image1 = [
+    [1,2,3],
+    [4,5,6],
+    [7,8,9]
+]
+solution.rotate(&image1)
+print("\(image1))")
+/** output
+ [
+ [7,4,1],
+ [8,5,2],
+ [9,6,3]
+ ]
+ */
+var image2 = [
+    [ 5, 1, 9,11],
+    [ 2, 4, 8,10],
+    [13, 3, 6, 7],
+    [15,14,12,16]
+]
+solution.rotate(&image2)
+print("\(image2)")
+/** output
+ [
+ [15,13, 2, 5],
+ [14, 3, 4, 1],
+ [12, 6, 8, 9],
+ [16, 7,10,11]
+ ]
+ */

Medium/0048-RotateImage.playground/Contents.swift

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