From 50a12ff215f7859b512e9f4fc7154196be0f56da Mon Sep 17 00:00:00 2001
From: qiuxuewei <qiuxuewei@baidu.com>
Date: Thu, 25 Nov 2021 16:24:01 +0800
Subject: [PATCH] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=20225.=20=E7=94=A8=E9=98=9F?=
 =?UTF-8?q?=E5=88=97=E5=AE=9E=E7=8E=B0=E6=A0=88=20Swift=E7=89=88=E6=9C=AC?=
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---
 problems/0225.用队列实现栈.md | 119 ++++++++++++++++++++++++++++
 1 file changed, 119 insertions(+)

diff --git a/problems/0225.用队列实现栈.md b/problems/0225.用队列实现栈.md
index edb88f36..be9f1f79 100644
--- a/problems/0225.用队列实现栈.md
+++ b/problems/0225.用队列实现栈.md
@@ -598,5 +598,124 @@ MyStack.prototype.empty = function() {
 
 ```
 
+Swift
+```Swift
+// 定义一个队列数据结构
+class Queue {
+    var array: [Int]
+    init() {
+        array = [Int]()
+    }
+    
+    /** Push element x to the back of queue. */
+    func push(_ x: Int) {
+        array.append(x)
+    }
+    
+    /** Removes the element from in front of queue and returns that element. */
+    func pop() -> Int {
+        if array.isEmpty {
+            return -1
+        }
+        return array.removeFirst()
+    }
+    
+    /** Get the front element. */
+    func peek() -> Int {
+        if array.isEmpty {
+            return -1
+        }
+        return array.first!
+    }
+    
+    /** Returns whether the queue is empty. */
+    func empty() -> Bool {
+        return array.isEmpty
+    }
+    
+    func count() -> Int {
+        return array.count
+    }
+}
+
+// 使用双队列
+class MyStack {
+    var queue1: Queue
+    var queue2: Queue
+    
+    init() {
+        queue1 = Queue()
+        queue2 = Queue()
+    }
+    
+    func push(_ x: Int) {
+        queue1.push(x)
+    }
+    
+    func pop() -> Int {
+        if queue1.empty() {
+            return -1
+        }
+        while queue1.count() > 1 {
+            queue2.push(queue1.pop())
+        }
+        let res = queue1.pop()
+        while !queue2.empty() {
+            queue1.push(queue2.pop())
+        }
+        return res
+    }
+    
+    func top() -> Int {
+        if queue1.empty() {
+            return -1
+        }
+        let res = pop()
+        push(res)
+        return res
+    }
+    
+    func empty() -> Bool {
+        return queue1.empty() && queue2.empty()
+    }
+}
+
+// 使用单队列
+class MyStack {
+    var queue: Queue
+    
+    init() {
+        queue = Queue()
+    }
+    
+    func push(_ x: Int) {
+        queue.push(x)
+    }
+    
+    func pop() -> Int {
+        if queue.empty() {
+            return -1
+        }
+        for _ in 1 ..< queue.count() {
+            queue.push(queue.pop())
+        }
+        return queue.pop()
+    }
+    
+    func top() -> Int {
+        if queue.empty() {
+            return -1
+        }
+        let res = pop()
+        push(res)
+        return res
+    }
+    
+    func empty() -> Bool {
+        return queue.empty()
+    }
+}
+```
+
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 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>