FatMouse‘ Trade

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.

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.

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

分析：按J[i]/F[i]的价值从大到小贪。

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<algorithm>
 4 using namespace std;
 5 const int maxn=1010;
 6 struct javabean{
 7     int j,f;
 8     double v;
 9 }value[maxn];
10 bool cmp(javabean a,javabean b){
11     return a.v>b.v;
12 }
13 int main()
14 {
15     int m,n;
16     while(scanf("%d%d",&m,&n)){
17         if(m==-1&&n==-1) break;
18         for(int i=0;i<n;i++){
19             scanf("%d%d",&value[i].j,&value[i].f);
20             value[i].v=(double)value[i].j/(value[i].f*1.0);
21         }
22         sort(value,value+n,cmp);
23         double sum=0.0;
24         for(int i=0;i<n;i++){
25             if(m>=value[i].f){
26                 sum+=value[i].j;
27                 m-=value[i].f;
28             }
29             else{
30                 sum+=value[i].v*m;
31                 break;
32             }
33         }
34         printf("%.3f\n",sum);
35     }
36     return 0;
37 }