[POJ] 3262 Protecting the Flowers.cpp

#include<cstdio>
#include<algorithm>
using namespace std;

struct cow{
    int T;
    int D;
};
bool cmp(cow a,cow b)
{
    return (a.D*1.0/a.T)>(b.D*1.0/b.T); //*1.0
}

int main()
{
    int N,i,j;
    long long sum=0,ans=0;  //long long int
    cow a[100001];
    while(scanf("%d",&N)!=EOF){
        for (i=0;i<N;i++){
            scanf("%d%d",&a[i].T,&a[i].D);
            sum+=a[i].D;
        }

        sort(a,a+N,cmp);
        
        for(i=0;i<N;i++){
            sum-=a[i].D;
            ans+=(sum*2*a[i].T);
        }
        printf("%lld\n",ans);
    }
    return 0;
}