代码随想录算法训练营第10天 |栈与队列part01：232.用栈实现队列，225. 用队列实现栈

注意实际上真实库函数的stack和queue的pop都是没有返回值的

#232

class MyQueue {
public:
    stack sin;
    stack sout;

    MyQueue() {
        //nothing, already initialized
        
    }
    
    void push(int x) {
        sin.push(x);
    }
    
    int pop() {
        //move sin to sout
        if(sout.empty()){
            while(!sin.empty()){
                int tmp=sin.top();
                sin.pop();
                sout.push(tmp);
        }

        }

        //pop first one in sout
        int res=sout.top();
        sout.pop();

        //move sout back to sin
        while(!sout.empty()){
            int tmp=sout.top();
            sout.pop();
            sin.push(tmp);
        }

        return res;
    }
    
    int peek() {
        /*
        //move sin to sout
        while(!sin.empty()){
            int tmp=sin.top();
            sin.pop();
            sout.push(tmp);
        }

        //top
        int res=sout.top();

        //move sout back to sin
        while(!sout.empty()){
            int tmp=sout.top();
            sout.pop();
            sin.push(tmp);
        }
        return res;
        */
        int res=this->pop();
        sout.push(res);



        return res;
        
    }
    
    bool empty() {
        return sin.empty()&&sout.empty();
    }
};

#225

class MyStack {
public:
    queue qin;
    queue qout;

    MyStack() {
        //do nothing, already do initialize
    }
    
    void push(int x) {
        qin.push(x);
    }
    
    int pop() {
        while(qin.size()>1){
            int tmp=qin.front();
            qin.pop();
            qout.push(tmp);
        }
        int res=qin.front();
        qin.pop();

        while(!qout.empty()){
            int tmp=qout.front();
            qout.pop();
            qin.push(tmp);
        }
        return res;
    }
    
    int top() {
        while(qin.size()>1){
            int tmp=qin.front();
            qin.pop();
            qout.push(tmp);
        }

        int res=qin.front();
        qin.pop();
        qout.push(res);

        while(!qout.empty()){
            int tmp=qout.front();
            qout.pop();
            qin.push(tmp);
        }
        return res;

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