Merge pull request #1076 from bqlin/master

优化版本，优化 Swift 版本实现

problems/1047.删除字符串中的所有相邻重复项.md

@@ -346,14 +346,12 @@ char * removeDuplicates(char * s){
 Swift：
 ```swift
 func removeDuplicates(_ s: String) -> String {
-    let array = Array(s)
     var stack = [Character]()
-    for c in array {
-        let last: Character? = stack.last
-        if stack.isEmpty || last != c {
-            stack.append(c)
-        } else {
+    for c in s {
+        if stack.last == c {
             stack.removeLast()
+        } else {
+            stack.append(c)
         }
     }
     return String(stack)