USACO Section 1.3.1 Mixing Milk

简单题,贪心,不多说

/*ID: zhuihun1PROG: milkLANG: C++*/#include <iostream>#include <fstream>#include <string.h>#include <stdio.h>#include<algorithm>#define MAXSIZE 20using namespace std;struct Farmer{    int price;    int amount;};int need,n;Farmer fa[5005];bool comp(Farmer a,Farmer b){    return a.price<b.price;}int main(){    ofstream fout ("milk.out");    ifstream fin ("milk.in");    int i;    fin>>need>>n;    for(i=0;i<n;i++)        fin>>fa[i].price>>fa[i].amount;    sort(fa,fa+n,comp);    int sum=0,cost=0;    i=0;    while(sum<need)    {        if(fa[i].amount+sum<need)        {            sum+=fa[i].amount;            cost+=fa[i].amount*fa[i].price;        }        else        {            cost+=fa[i].price*(need-sum);            sum=need;        }        i++;    }    fout<<cost<<endl;    return 0;}