# 【bzoj1634】[Usaco2007 Jan]Protecting the Flowers 护花 贪心

Farmer John went to cut some wood and left N (2 <= N <= 100,000) cows eating the grass, as usual. When he returned, he found to his horror that the cows were in his garden eating his beautiful flowers. Wanting to minimize the subsequent damage, FJ decided to take immediate action and transport the cows back to their barn. Each cow i is at a location that is Ti minutes (1 <= Ti <= 2,000,000) away from the barn. Furthermore, while waiting for transport, she destroys Di (1 <= Di <= 100) flowers per minute. No matter how hard he tries,FJ can only transport one cow at a time back to the barn. Moving cow i to the barn requires 2*Ti minutes (Ti to get there and Ti to return). Write a program to determine the order in which FJ should pick up the cows so that the total number of flowers destroyed is minimized.

* Line 1: A single integer

N * Lines 2..N+1: Each line contains two space-separated integers, Ti and Di, that describe a single cow's characteristics

* Line 1: A single integer that is the minimum number of destroyed flowers

6
3 1
2 5
2 3
3 2
4 1
1 6

86

#include <cstdio>
#include <algorithm>
using namespace std;
struct data
{
int t , d;
}a[100005];
long long sum[100005];
bool cmp(data a , data b)
{
return a.t * b.d < a.d * b.t;
}
int main()
{
int n , i;
long long ans = 0;
scanf("%d" , &n);
for(i = 1 ; i <= n ; i ++ )
scanf("%d%d" , &a[i].t , &a[i].d);
sort(a + 1 , a + n + 1 , cmp);
for(i = n ; i >= 1 ; i -- )
sum[i] = sum[i + 1] + a[i].d;
for(i = 1 ; i <= n ; i ++ )
ans += 2 * sum[i + 1] * a[i].t;
printf("%lld\n" , ans);
return 0;
}
posted @ 2017-01-12 16:11  GXZlegend  阅读(211)  评论(0编辑  收藏  举报