[Array] Update to Swift 3.0

Author: Yi Gu

Array/MaximumSizeSubarraySumEqualsK.swift

@@ -5,21 +5,20 @@
  */
 
 class MaximumSizeSubarraySumEqualsK {
-    func maxSubArrayLen(nums: [Int], _ k: Int) -> Int {
-        var longestLen = 0
-        var dict = [Int: Int]()
-        dict[0] = -1
-        var sum = 0
+    func maxSubArrayLen(_ nums: [Int], _ k: Int) -> Int {
+        var longestLen = 0, sum = 0
+        var sumToIdx = [Int: Int]()
+        sumToIdx[0] = -1
 
-        for i in 0 ..< nums.count {
-            sum += nums[i]
+        for (i, num) in nums.enumerated() {
+            sum += num
 
-            if let lastIndex = dict[sum - k] {
-                longestLen = max(longestLen, i - lastIndex)
+            if let idx = sumToIdx[sum - k] {
+                longestLen = max(longestLen, i - idx)
             }
 
-            guard let index = dict[sum] else {
-                dict[sum] = i
+            guard let idx = sumToIdx[sum] else {
+                sumToIdx[sum] = i
                 continue
             }
         }

Array/MoveZeroes.swift

@@ -1,24 +1,25 @@
 /**
  * Question Link: https://leetcode.com/problems/move-zeroes/
- * Primary idea: keep index zeroIndex, traverse through the array and swap the value
+ * Primary idea: keep index for element not equal to 0, traverse and set up the index
  *
  * Time Complexity: O(n), Space Complexity: O(1)
  *
  */
 
 class MoveZeroes {
     func moveZeroes(_ nums: inout [Int]) {
-        var zeroIndex = 0
-  
-        for i in 0 ..< nums.count {
-            if nums[i] != 0 {
-                _swap(&nums, i, zeroIndex)
-                zeroIndex += 1
+        var idx = 0
+        
+        for (i, num) in nums.enumerated() {
+            if num != 0 {
+                nums[idx] = num
+                idx += 1
             }
         }
-    }
-
-    private func _swap<T>(_ nums: inout Array<T>, _ p: Int, _ q: Int) {
-        (nums[p], nums[q]) = (nums[q], nums[p])
+        
+        while idx < nums.count {
+            nums[idx] = 0
+            idx += 1
+        }
     }
 }