leetcode 225.用队列实现栈

class MyStack {
public:
    queue<int> que1;
    queue<int> que2;
    MyStack() {
        
    }
    
    void push(int x) {
        que1.push(x);
    }
    
    int pop() {
        int len=que1.size();
        len--;
        while(len--){
            que2.push(que1.front());
            que1.pop();
        }
        int temp=que1.front();
        que1.pop();
        que1=que2;
        while(!que2.empty()){
            que2.pop();
        }
        return temp;
    }
    
    int top() {
        int len=que1.size();
        len--;
        while(len--){
            que2.push(que1.front());
            que1.pop();
        }
        int temp=que1.front();
        que1.pop();
        que2.push(temp);
        que1=que2;
        while(!que2.empty()){
            que2.pop();
        }
        return temp;  
    }
    
    bool empty() {
        return que1.empty();
    }
};

/**
 * 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();
 * bool param_4 = obj->empty();
 */