【用队列实现栈】【用栈实现队列】Leetcode 232 225

---------------🎈🎈题目链接 用队列实现栈🎈🎈-------------------
---------------🎈🎈题目链接 用栈实现队列🎈🎈-------------------

队列的相关操作

创建队列
Queue<Integer> myqueue = new LinkedList<>();
添加元素
myqueue.add();
队列最初的元素
myqueue.peek();
队列弹出元素：
myqueue.poll();
队列大小
myqueue.size();
队列是否为空
myqueue.isEmpty();

栈的相关操作

创建栈
Stack<Integer> mystack = new Stack<>();
添加元素
mystack.push();
栈顶元素
mystack.peek();
弹出栈顶元素：
mystack.pop();
栈大小
mystack.size();
栈是否为空
mystack.isEmpty();

用队列实现栈

class MyStack {Queue<Integer> myqueue;public MyStack() {myqueue = new LinkedList<>();}public void push(int x) {myqueue.add(x);}public int pop() {for(int i = 0; i < myqueue.size()-1; i++){myqueue.add(myqueue.poll());}return myqueue.poll();}public int top() {int top;for(int i = 0; i < myqueue.size()-1; i++){myqueue.add(myqueue.poll());}top = myqueue.peek();myqueue.add(myqueue.poll());return top;}public boolean empty() {if(myqueue.isEmpty()){return true;}else return false;}
}/*** Your MyStack object will be instantiated and called as such:* MyStack obj = new MyStack();* obj.push(x);* int param_2 = obj.pop();* int param_3 = obj.top();* boolean param_4 = obj.empty();*/

用栈实现队列

class MyQueue {Stack<Integer> mystackin;Stack<Integer> mystackout;public MyQueue() {mystackin = new Stack<>();mystackout = new Stack<>();}public void push(int x) {while(!mystackout.isEmpty()){mystackin.push(mystackout.pop());}mystackin.push(x);}public int pop() {while(!mystackin.isEmpty()){mystackout.push(mystackin.pop());}return mystackout.pop();}public int peek() {while(!mystackin.isEmpty()){mystackout.push(mystackin.pop());}return mystackout.peek();}public boolean empty() {if(mystackin.isEmpty() && mystackout.isEmpty()){return true;}else return false;}
}/*** Your MyQueue object will be instantiated and called as such:* MyQueue obj = new MyQueue();* obj.push(x);* int param_2 = obj.pop();* int param_3 = obj.peek();* boolean param_4 = obj.empty();*/