B1020（25）

本题坑点大概在除了n以外其他的数据都有可能是浮点数，所以最好都用double类型，涉及到产品数量总量和单价，所以采用结构体来实现

#include<cstdio>
#include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;
const int maxn=1001;
struct node
{
	double totalprice;
	double totalnum;
	double perprice;
}a[maxn];
bool cmp (node b,node c)
{
	return b.perprice>c.perprice;
}
int main()
{
      int n;
      double m,total=0;
      cin>>n>>m;
      for (int i=0;i<n;i++)
      scanf("%lf",&a[i].totalnum);
      for (int i=0;i<n;i++)
      {
      	scanf("%lf",&a[i].totalprice);
      	a[i].perprice=a[i].totalprice/a[i].totalnum;
	  }
	  sort (a,a+n,cmp);
	  for (int i=0;i<n;i++)
	  {
	  	double temp=a[i].totalnum-m;
		  if (temp>0)
	    	{
	  		total+=m*a[i].perprice;
	  		break;
		  }
		  else
		 {
		 	total+=a[i].totalnum*a[i].perprice;
		 	m-=a[i].totalnum;
		 }
	  }
	  printf("%.2f",total);
}