Solutions to [Stack] [Array]

Array/RemoveDuplicatesFromSortedArray.swift

@@ -6,18 +6,17 @@
  */
 
 class RemoveDuplicatesFromSortedArray {
-    func removeDuplicates(inout nums: [Int]) -> Int {
-        guard nums.count > 0 else {
-            return 0
-        }
-
-        var index = 0
+    func removeDuplicates(_ nums: inout [Int]) -> Int {
+        if nums.isEmpty { return 0 }
 
-        for num in nums where num != nums[index] {
-            index += 1
-            nums[index] = num
+        var i = 0
+        for j in 1..<nums.count {
+            if nums[i] != nums[j] {
+                nums[i + 1] = nums[j]
+                i += 1
+            }
         }
 
-        return index + 1
+        return i + 1
     }
-}
+}

Array/RemoveElement.swift

@@ -6,8 +6,8 @@
  */
 
 class RemoveElement {
-    func removeElement(inout nums: [Int], _ val: Int) -> Int {
-        nums = nums.filter { (num) in num != val }
+    func removeElement(_ nums: inout [Int], _ val: Int) -> Int {
+        nums = nums.filter { $0 != val }
         return nums.count
     }
-}
+}

Stack/ValidParentheses.swift

@@ -12,20 +12,20 @@ class ValidParentheses {
             if char == "(" || char == "[" || char == "{" {
                 stack.append(char)
             } else if char == ")" {
-                guard stack.count != 0 && stack.removeLast() == "(" else {
+                guard stack.popLast() == "(" else {
                     return false
                 }
             } else if char == "]" {
-                guard stack.count != 0 && stack.removeLast() == "[" else {
+                guard stack.popLast() == "[" else {
                     return false
                 }
             } else if char == "}" {
-                guard stack.count != 0 && stack.removeLast() == "{" else {
+                guard stack.popLast() == "{" else {
                     return false
                 }
             }
         }
 
         return stack.isEmpty
     }
-}
+}