学步园

题目：http://pat.zju.edu.cn/contests/pat-a-practise/1070

题解：

代码：

#include<cstdio>
#include<iostream>
#include<cstring>
#include<cmath>
#include<string>
#include<vector>
#include<algorithm>
using namespace std;
struct moonCake
{
    double n;
    double price;
}cake[2005];
bool cmp(const struct moonCake &a,const struct moonCake &b)
{
    return a.price>b.price;
}
int main()
{
    int n;
    double summ,getx=0;
    scanf("%d%lf",&n,&summ);
    for(int i=0;i<n;++i)
        scanf("%lf",&cake[i].n);
    for(int i=0;i<n;++i)
    {
        scanf("%lf",&cake[i].price);
        if(cake[i].n>0)
        {
            cake[i].price=cake[i].price/cake[i].n;
        }
        else
            cake[i].price=0;
    }
    sort(cake,cake+n,cmp);
    for(int i=0;i<n&&summ>0;++i)
    {
        if(summ>=cake[i].n)
        {
            getx+=(cake[i].price*cake[i].n);
            summ-=cake[i].n;
        }
        else
        {
            getx+=(summ*cake[i].price);
            summ=0;
        }
    }
    printf("%.2f\n",getx);
    return 0;
}

来源：http://blog.csdn.net/acm_ted/article/details/20147861