【PAT】PAT Advanced 1006 Sign In and Sign Out

At the beginning of every day, the first person who signs in the computer room will unlock the door, and the last one who signs out will lock the door. Given the records of signing in’s and out’s, you are supposed to find the ones who have unlocked and locked the door on that day.

Input Specification:

Each input file contains one test case. Each case contains the records for one day. The case starts with a positive integer M, which is the total number of records, followed by M lines, each in the format:

ID_number Sign_in_time Sign_out_time
where times are given in the format HH:MM:SS, and ID_number is a string with no more than 15 characters.

Output Specification:

For each test case, output in one line the ID numbers of the persons who have unlocked and locked the door on that day. The two ID numbers must be separated by one space.

Note: It is guaranteed that the records are consistent. That is, the sign in time must be earlier than the sign out time for each person, and there are no two persons sign in or out at the same moment.

Sample Input:

3
CS301111 15:30:28 17:00:10
SC3021234 08:00:00 11:25:25
CS301133 21:45:00 21:58:40

Sample Output:

SC3021234 CS301133

题目大意

最先进机房的学生需要开门，最后出机房的学生需要关门，输出这两个学生的学号。

思路

不需要记录所有学生的信息，每输入一个学生的进出时间，更新即可。

//
//  main.cpp
//  PAT1006
//
//  Created by 许少钧 on 2019/4/8.
//  Copyright © 2019年 许少钧. All rights reserved.
//
#include <iostream>
#include <climits>
using namespace std;
int main() {
    int n, minN = INT_MAX, maxN = INT_MIN;
    scanf("%d", &n);
    string unlocked, locked;
    int in, out;
    for(int i = 0; i < n; i++) {
        string t;
        cin >> t;
        int h1, m1, s1, h2, m2, s2;
        scanf("%d:%d:%d %d:%d:%d", &h1, &m1, &s1, &h2, &m2, &s2);
        in = h1 * 3600 + m1 * 60 + s1;
        out = h2 * 3600 + m2 * 60 + s2;
        if (in < minN) {
            minN = in;
            unlocked = t;
        }
        if (out > maxN) {
            maxN = out;
            locked = t;
        }
    }
    cout << unlocked << " " << locked;
    return 0;
}