模拟队列

(模拟队列) $O(n)$

C++ 代码

#include <iostream>
#include <string>
using namespace std;

const int N = 100010;
int q[N];
int hh = 0, ll = 0;
int main()
{
    cin.tie(0);
    std::ios::sync_with_stdio(false);
    string command;
    int num, temp;
    cin >> num;
    while(num--)
    {
        cin >> command;
        if(command == "push")
        {
            cin >> temp;
            q[ll++] = temp; 
        }
        else if(command == "pop")
        {
            if(ll != hh)
                hh++;
        }
        else if(command == "empty")
        {
            if(ll == hh)
                cout << "YES" << endl;
            else
                cout << "NO" << endl;
        }
        else
        {
            if(ll != hh)
            cout << q[hh] << endl;
        }
    }
    return 0;
}