PAT甲级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

题目要求：

每天，第一个登录电脑的人开门，最后一个退出电脑的人关门；已知每个人登录和退出电脑的时间，需要找出开门的人和关门的人；

输入包括记录的条数，以及每个人的ID、登录、退出时间；ID字符串不超过15个字符，时间输入格式为HH:MM:SS；

输出要求：输出开门的人和关门的人ID，ID之间使用空格隔开；

题目的输入保证每个人登录时间早于退出时间，并且没有任何两个人的登录退出时间是相同的；

解题思路

方法一：直接使用int strcmp(const char *str1, const char *str2)比较输入的登录时间与输出时间的字符串的大小,因为数字对应的ASCII码是由小至大，所以可以用字符比较的方式，下面的代码即为方法一

#include "stdio.h"#include "stdlib.h"#include "string.h"#include "stdbool.h"typedef struct user {    char name[20];    char inTime[20];    char outTime[20];}user;int main() {    user user[100];    int num;    int unLockedIndex;    int lockedIndex;    char inTimeTmp[20];    strcpy(inTimeTmp,"23:59:59");    char outTimeTmp[20];    strcpy(outTimeTmp, "00:00:00");    unLockedIndex = 0;    lockedIndex = 0;    scanf("%d",&num);    for (int i = 0; i < num; i++)    {        scanf("%s",&user[i].name);        scanf("%s", &user[i].inTime);        //大于零表示第二个字符串小于第一个        if (strcmp(inTimeTmp, user[i].inTime)>0)        {            strcpy(inTimeTmp, user[i].inTime);            unLockedIndex = i;        }        scanf("%s", &user[i].outTime);        //表示第二个字符串大于第一个        if (strcmp(outTimeTmp, user[i].outTime)<0)            {                strcpy(outTimeTmp, user[i].outTime);                lockedIndex = i;            }    }    printf("%s %s",user[unLockedIndex].name,user[lockedIndex].name);    system("pause");    return 0;}