Leetcode—232. 用栈实现队列【简单】

2024每日刷题（131）

Leetcode—232. 用栈实现队列

在这里插入图片描述

实现代码

class MyQueue {
public:
    MyQueue() {

    }
    
    void push(int x) {
        st.push(x);
    }
    
    int pop() {
        if(show.empty()) {
            if(empty()) {
                return -1;
            } else {
                int ans = show.top();
                show.pop();
                return ans;
            }
        } else {
            int ans = show.top();
            show.pop();
            return ans;
        }
    }
    
    int peek() {
        if(show.empty()) {
            if(empty()) {
                return -1;
            } else {
                return show.top();
            }
        } else {
            return show.top();
        }
    }
    
    bool empty() {
        if(show.empty()) {
            if(st.empty()) {
                return true;
            } else {
                while(!st.empty()) {
                    show.push(st.top());
                    st.pop();
                }
                return false;
            }
        } else {
            return false;
        }
    }
private:
    stack<int> st;
    stack<int> show;
};

/**
 * 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();
 */