AcWing 829. 模拟队列

# 模拟队列

#include <iostream>

using namespace std;

const int N = 1e5 + 10;

int q[N], hh, tt = -1;

void push(int x){
    q[++tt] = x;
}

void pop(){
    hh++;
}

void empty(){
    if(hh <= tt) cout << "NO" << endl;
    else cout << "YES" << endl;
}

void query(){
    cout << q[hh] << endl;
}

int main(){
    int m;
    cin >> m;
    while(m--){
        string s;
        cin >> s;
        if(s == "push"){
            int x;
            cin >> x;
            push(x);
        }
        else if(s == "empty"){
            empty();
        }
        else if(s == "query"){
            query();
        }
        else{
            pop();
        }
    }

    return 0;
}

# 队列

//在队尾插入元素，在队头弹出元素
int q[N], hh, tt = -1;

//插入
q[++tt] = x;

//弹出
hh++;

//判断队列是否为空
if(hh <= tt) not empty;