贪心/hdu 1009 FatMouse' Trade

 1 /*
 2     PROBLEM:hdu1009
 3     AUTHER:Nicole Lam
 4     MEMO:贪心
 5 */
 6 
 7 #include<cstdio>
 8 #include<algorithm>
 9 using namespace std;
10 
11 
12 struct xx
13 {
14     double j,f,price;
15 };
16 xx x[1010];
17 
18 
19 
20 bool cmp(xx a,xx b)
21 {
22     if (a.price <= b.price) return true;
23     return false;
24 }
25 
26 
27 int main()
28 {
29     int m,n;
30     scanf("%d%d",&m,&n);
31     while ( m!=-1  &&  n!=-1)
32     {
33         for (int i=1;i<=n;i++)
34         {
35             scanf("%lf%lf", &x[i].j, &x[i].f);
36             x[i].price = x[i].f / x[i].j;
37         }
38         sort(x+1,x+1+n,cmp);
39 
40         double ans = 0;
41 
42         for (int i=1;i<=n;i++)
43         {
44             if (m>=x[i].f)
45             {
46                 m-=x[i].f;
47                 ans+=x[i].j;
48             }
49             else
50             {
51                 ans+=m*x[i].j/x[i].f;
52                 m=0;
53                 break;
54             }
55         }
56         printf("%.3lf\n",ans);
57         scanf("%d%d", &m, &n);
58     }
59     return 0;
60 }