方法1：只用一個隊列
出棧直接出隊，但是入棧前先直接入隊，然后出隊n-1個元素并入隊，這樣剛進隊的元素就在隊頭了。
上代碼：

class MyStack {private Queue<Integer> queue=new LinkedList<>();/** Initialize your data structure here. */public MyStack() {}/** Push element x onto stack. */public void push(int x) {queue.add(x);for(int i=1;i<queue.size();i++){queue.add(queue.poll());}}/** Removes the element on top of the stack and returns that element. */public int pop() {return queue.poll();}/** Get the top element. */public int top() {return queue.peek();}/** Returns whether the stack is empty. */public boolean empty() {return queue.isEmpty();}}

方法二：采用兩個隊helpQ和pollQ
入棧時先將pollQ的元素出隊并存入helpQ中，然后新元素進pollQ，再將helpQ中的所有元素出隊依次進pollQ
代碼：

class MyStack {private Queue<Integer> pollQ=new LinkedList<>(); private Queue<Integer> helpQ=new LinkedList<>();/** Initialize your data structure here. */public MyStack() {}/** Push element x onto stack. */public void push(int x) {while(!pollQ.isEmpty()){helpQ.add(pollQ.poll());}pollQ.add(x);while(!helpQ.isEmpty()){pollQ.add(helpQ.poll());}}/** Removes the element on top of the stack and returns that element. */public int pop() {return pollQ.poll();}/** Get the top element. */public int top() {return pollQ.peek();}/** Returns whether the stack is empty. */public boolean empty() {return pollQ.isEmpty();}}

如有錯誤，請指正！

總結

以上是生活随笔為你收集整理的LeetCode225. Implement Stack using Queues的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。