Dec 7, 2021 · Oct 12, 2021 · Oct 12, 2021 · Oct 12, 2021 · Oct 12, 2021 · Oct 12, 2021
diff --git a/problems/0225.用队列实现栈.md b/problems/0225.用队列实现栈.md
Original file line number	Diff line number	Diff line change
Expand Up		@@ -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()
	}
	}
	```

		-----------------------
		<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>