232.用栈实现队列

力扣题目链接

文章讲解

问题不大，今天的内容没啥好讲的，整体就是从kmp的阴影中过度一下~

#include <iostream>
#include <queue>
using namespace std;
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--) {
            // que1导入que2，留下的最后一个元素是等待返回的元素
            que2.push(que1.front());
            que1.pop();
        }
        // 等待返回的元素
        int result = que1.front();
        que1.pop();
        que1 = que2;
        // 清空辅助栈
        while (!que2.empty()) {
            que2.pop();
        }
        return result;
    }
    
    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();
 */

225. 用队列实现栈

力扣题目链接

文章讲解

#include <iostream>
#include <stack>
using namespace std;
class MyQueue {
public:
    stack<int> stIn;
    stack<int> stOut;
    MyQueue() {

    }
    
    void push(int x) {
        stIn.push(x);
    }
    
    int pop() {
        // 只有当stOut为空的时候，再从stIn导入数据（全部）
        if (stOut.empty()) {
            while (!stIn.empty()) {
                stOut.push(stIn.top());
                stIn.pop();
            }
        }
        int result = stOut.top();
        stOut.pop();
        return result;
    }
    
    int peek() {
        int res = this->pop();
        // pop函数弹出了元素res，所以再添加回去
        stOut.push(res);
        return res;
    }
    
    bool empty() {
        return stIn.empty() && stOut.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();
 */