代码随想录第二十八天

字符串-用队列实现栈

题目链接

class MyStack {
public:
    queue<int> que1;
    queue<int> que2;
    MyStack() {

    }
    
    void push(int x) {
        que1.push(x);
    }
    
    int pop() {
        int size = que1.size();
        size--;
        while(size--){
            que2.push(que1.front());//如果用单队列实现，可以直接que1.push(que1.front())
            que1.pop();
        }

        int res = que1.front();
        que1.pop();
        que1 = que2;
        while(!que2.empty())que2.pop();

        return res;
    }
    
    int top() {
        return que1.back();
    }
    
    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();
 */