算法刷题Day 10 用栈实现队列+用队列实现栈-Toy模板网

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Day 10 栈和队列

用栈实现队列

class MyQueue {
    stack<int> stk1, stk2;
public:
    MyQueue() {
        
    }
    
    void push(int x) {
        stk1.push(x);
    }
    
    int pop() {
        if (stk2.empty())
        {
            while (!stk1.empty())
            {
                stk2.push(stk1.top());
                stk1.pop();
            }
        }
        int ret = stk2.top();
        stk2.pop();

        return ret;
    }
    
    int peek() {
        if (stk2.empty())
        {
            while (!stk1.empty())
            {
                stk2.push(stk1.top());
                stk1.pop();
            }
        }

        return  stk2.top();
    }
    
    bool empty() {
        return stk1.empty() && stk2.empty();
    }
};

/**
 * 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();
 */

225. 用队列实现栈

之前做过，但现在还是卡壳了，想了有一会儿才想出来。

其实使用一个队列就可以实现栈文章来源地址https://www.toymoban.com/news/detail-564781.html

class MyStack {
    queue<int> que;

public:
    MyStack() {
        
    }
    
    void push(int x) {
        que.push(x);
    }
    
    int pop() {
        int time = que.size();
        while (--time)
        {
            que.push(que.front());
            que.pop();
        }
        int ret = que.front();
        que.pop();

        return ret;
    }
    
    int top() {
        int time = que.size();
        while (--time)
        {
            que.push(que.front());
            que.pop();
        }
        int ret = que.front();
        que.push(que.front());
        que.pop();

        return ret;
    }
    
    bool empty() {
        return que.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();
 */