1006. Sign In and Sign Out

pat甲级

思路： 读入每个人的到达和离开时间，求最早到达的人和最后一个离开的人。本来是时间比较，由于时间格式的原因，可以直接当作字符串进行比较。

训练： 字符串

题目描述：

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:

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

Sample Output:

SC3021234 CS301133

参考代码：

#include <iostream>#include <string>using namespace std;int main(){  freopen("in.txt","r",stdin);  int n;  while(cin>>n)  {  string unlockTime,lockTime,unlockPerson,lockPerson;  cin>>unlockPerson>>unlockTime>>lockTime;  lockPerson=unlockPerson;  for(int i=1;i<n;i++)  {  string id,signIn,signOut;  cin>>id>>signIn>>signOut;  if (signIn<unlockTime)  unlockTime=signIn,unlockPerson=id;  if (signOut>lockTime)  lockTime=signOut,lockPerson=id;  }  cout<<unlockPerson<<" "<<lockPerson<<endl;  }  return 0;}