本题关键：两个比较的时间位数相同，所以可以用字典序排序

y总code：
老师是在循环里面的判断条件写的if (!i || in_time < first_time)
!i：先把第一个人记录成结果 （好聪明啊hh）

#include<iostream>

using namespace std;

int main()
{
    int n;
    string id, in_time, out_time; 
    string first_id, last_id;
    string first_time, last_time;

    cin >> n;

    for (int i = 0; i < n; i ++ )
    {
        cin >> id >> in_time >> out_time;

        if (!i || in_time < first_time) 
        {
            first_id = id;
            first_time = in_time;
        }

        if (!i || out_time > last_time)
        {
            last_id = id;
            last_time = out_time;
        }
    }

    cout << first_id << ' ' << last_id << endl;

    return 0;
}

我的code：
我是在循环外面 先把第一个人的出入时间记成结果，然后更新！

#include<iostream>

using namespace std;

int main()
{
    int n;
    string id, in_time, out_time; 
    string first_id, last_id;
    string first_time, last_time;

    cin >> n;
    cin >> id >> first_time >> last_time;

    first_id= id;
    last_id = id;

    for (int i = 1; i < n; i ++ )
    {
        cin >> id >> in_time >> out_time;



        if (i && in_time < first_time) 
        {
            first_id = id;
            first_time = in_time;
        }

        if (i && out_time > last_time)
        {
            last_id = id;
            last_time = out_time;
        }
    }

    cout << first_id << ' ' << last_id << endl;

    return 0;
}