struct数组用错，而且这个题不用考虑分母为0，还不报错，奇了怪了！！！
Problem Description
FatMouse prepared M pounds of cat food, ready to trade with the cats guarding the warehouse containing his favorite food, JavaBean.
The warehouse has N rooms. The i-th room contains J[i] pounds of JavaBeans and requires F[i] pounds of cat food. FatMouse does not have to trade for all the JavaBeans in the room, instead, he may get J[i]* a% pounds of JavaBeans if he pays F[i]* a% pounds of
cat food. Here a is a real number. Now he is assigning this homework to you: tell him the maximum amount of JavaBeans he can obtain.
The warehouse has N rooms. The i-th room contains J[i] pounds of JavaBeans and requires F[i] pounds of cat food. FatMouse does not have to trade for all the JavaBeans in the room, instead, he may get J[i]* a% pounds of JavaBeans if he pays F[i]* a% pounds of
cat food. Here a is a real number. Now he is assigning this homework to you: tell him the maximum amount of JavaBeans he can obtain.
Input
The input consists of multiple test cases. Each test case begins with a line containing two non-negative integers M and N. Then N lines follow, each contains two non-negative integers J[i] and F[i] respectively. The last test case
is followed by two -1's. All integers are not greater than 1000.
is followed by two -1's. All integers are not greater than 1000.
Output
For each test case, print in a single line a real number accurate up to 3 decimal places, which is the maximum amount of JavaBeans that FatMouse can obtain.
Sample Input
5 3 7 2 4 3 5 2 20 3 25 18 24 15 15 10 -1 -1
Sample Output
13.333 31.500
#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
struct point
{
double x,y;
double bl;
}points[1001];
int cp(const void *a,const void *b)
{
struct point *c=(point *)a;
struct point *d=(point *)b;
if(c->bl<=d->bl) return 1;
else return -1;//这儿是-1而不是0
}
int main()
{
int n,m;
while(scanf("%d%d",&n,&m))
{
if(m==-1&&n==-1) break;
for(int i=0;i<m;i++)
{
scanf("%lf %lf",&points[i].x,&points[i].y);
points[i].bl=points[i].x/points[i].y;
}
qsort(points,m,sizeof(points[0]),cp);
double sum=0.0;
for(int j=0;j<m;j++)
{
if(n>=points[j].y)
{
sum+=points[j].x;
n-=points[j].y;
}
else
{
sum+=n*points[j].x/points[j].y;
break;
}
}
printf("%.3lf\n",sum);
}
return 0;
}