hdu 1009 简单贪心

#include <stdio.h>
#include <stdlib.h>
struct node
{
int i,j;
double p;
} s[1000];
int cmp (const void *a,const void *b)
{
struct node*aa=( struct node*)a;
struct node*bb=(struct node*)b;
return (((aa->p)<(bb->p))?1:-1);
}
int main ()
{
int m,n,i,j;
double sum;
while (~scanf("%d%d",&m,&n))
{
sum=0;
if(m==-1&&n==-1)
break;
for(i=0; i<n; i++)
{
scanf("%d%d",&s[i].i,&s[i].j);
s[i].p=(double)s[i].i/s[i].j;
}
qsort (s,n,sizeof(s[0]),cmp);
for(i=0;i<n;i++)
{
if(m>s[i].j)
{
sum+=s[i].i;
m-=s[i].j;
}
else
{
sum+=(double)(m*s[i].p);
//m=0;
break;
}

}
printf("%.3lf\n",sum);
}
return 0;
}