題目鏈接：Average is not Fast Enough!

 1 #include <iostream>
 2 #include <cstring>
 3 #include <string>
 4 #include <cstdio>
 5 using namespace std;
 6 int main() 
 7 {
 8     int n, id;
 9     double d;
10     cin>>n>>d;
11     while (cin>>id) {
 
12         printf("%3d: ", id);
13         int mark = 0;
14         int time = 0;
15         for (int i=0; i<n; i++) {
16             string str;
17             cin>>str;
18             if (str[0] == ‘-‘) {
19                 mark = 1;
20 //                printf("-\n");不能在這裏輸出，因為會碰到多個不及格的，WA了數次 
 

21             }
22             if(mark==1)continue;
23             time += (str[0]-‘0‘) * 3600+ ((str[2]-‘0‘)*10+(str[3]-‘0‘)) * 60 + (str[5]-‘0‘)*10+(str[6]-‘0‘);
24         }
25         if (mark == 1) {
26             printf("-\n");
27             continue;
28         }
29         double a = time / d;
 
30         int t = (int)(a + 0.5);
31         printf("%d:%02d min/km\n", t/60, t%60);
32     }
33     return 0;
34 }

hdoj-1036-Average is not Fast Enough!(水題，坑)