POJ 3262 Protecting the flowers

 1 #include <iostream>
 2 #include <stdio.h>
 3 #include <algorithm>
 4 using namespace std;
 5 
 6 
 7 int n;
 8 struct Cow
 9 {
10     double t, d;
11     bool operator < (Cow a) const
12     {
13         return t / d < a.t / a.d;
14     }
15 }cow[100007];
16 int main()
17 {
18     freopen("in.txt", "r", stdin);
19     while(~scanf("%d", &n))
20     {
21         long long ans = 0, sum = 0;
22         for (int i = 0; i < n; i++)
23         {
24             scanf("%lf%lf", &cow[i].t, &cow[i].d);
25             sum += cow[i].d;
26         }
27         sort(cow, cow+n);
28         for (int i = 0; i < n; i++)
29         {
30             sum -= cow[i].d;
31             ans += sum*cow[i].t*2;
32             //printf("%.0lf %.0lf\n", cow[i].t, cow[i].d);
33         }
34         printf("%lld\n", ans);
35     }
36     return 0;
37 }