算法知识点————两个栈实现一个队列

思路：当队列入队的时候，将元素入栈（instack），当队列出栈的时候，先判断栈（outstack）是否为空，如果为空，则将栈（instack）的元素全部放入栈（outstack）中，然后取出栈（outstack）顶元素；如果栈（outstack）不为空，则直接取出栈（outstack）顶元素。

class MyQueue {
private: stack<int> instack,outstack;void inout(){while(!instack.empty()){outstack.push(instack.top());instack.pop();}}public:MyQueue() {}void push(int x) {instack.push(x);}int pop() {if(outstack.empty()){inout()；}int x = outstack.top();outstack.pop();return x;}int peek() {if(outstack.empty()){inout()；}return outstack.top();}bool empty() {return instack.empty() && outstack.empty();}
};/*** 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();* bool param_4 = obj->empty();*/