HDU1009 

 1 #include<stdio.h>
 2 #include<stdlib.h>
 3 struct gg
 4 {
 5     int j;
 6     int f;
 7     double p;
 8 }gl[1005],tp;
 9 int cmp(const void *a,const void *b)
10 {
11     return (*(struct gg*)b).p>(*(struct gg*)a).p?1:-1;
12 }
13 int main()
14 {
15     int m,n,i;
16     double left,sum;
17     while(scanf("%d%d",&m,&n)==2&&(m!=-1)&&(n!=-1))
18     {
19         for(i=0;i<n;i++)
20         {
21             scanf("%d%d",&gl[i].j,&gl[i].f);
22             gl[i].p=1.0*gl[i].j/gl[i].f;
23         }
24         qsort(gl,n,sizeof(gl[0]),cmp);
25         left=m*1.0;
26         sum=0.0;
27         for(i=0;i<n&&left>=0;i++)
28         {
29             if(left>=gl[i].f)
30             {
31                 sum=sum+1.0*gl[i].j;
32                 left=left-1.0*gl[i].f;
33                 //if(left==0)break;
34             }
35             else
36                 if(left>=0&&left<gl[i].f)
37             {
38                 sum=sum+(gl[i].p)*left;
39                 left=left-(gl[i].p)*left;
40                 //left=0;
41                 //break;
42             }
43         }
44         printf("%.3lf\n",sum);
45     }
46     return 0;
47 }
posted @ 2012-04-26 23:00  xxx0624  阅读(473)  评论(0)  编辑  收藏  举报