代码随想录算法训练营第十天|232.用栈实现队列225. 用队列实现栈

232.用栈实现队列

class MyQueue {
public:
    stack<int>in;
    stack<int>out;
    MyQueue() {

    }
    
    void push(int x) {
        in.push(x);
    }
    
    int pop() {
        if(out.empty()){
            while(!in.empty()){
                out.push(in.top());
                in.pop();
            }
        }
        int a=out.top();
        out.pop();
        return a;
    }
    
    int peek() {
        int ans=this->pop();
        out.push(ans);
        return ans;
    }
    
    bool empty() {
        return in.empty()&&out.empty();
    }
};

225. 用队列实现栈

class MyStack {
public:
    queue<int> a;
    MyStack() {}

    void push(int x) { a.push(x); }

    int pop() {
        int len = a.size() - 1;
        while (len > 0) {
            a.push(a.front());
            a.pop();
            len--;
        }
        int z = a.front();
        a.pop();
        return z;
    }

    int top() { return a.back(); }

    bool empty() { return a.empty(); }
};