FatMouse

时间限制：1 秒

内存限制：128 兆

特殊判题：否

提交：1431

解决：641

题目描述：

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.

输入：

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.

输出：

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.

样例输入：

5 3
7 2
4 3
5 2
20 3
25 18
24 15
15 10
-1 -1

样例输出：

13.333
31.500

 1 #include <iostream>
 2 #include <algorithm>
 3 #include <iomanip>
 4 using namespace std;
 5  
 6 struct goods
 7 {
 8    int J,F;
 9    double xinjia;
10 }buf[1000];
11  
12  
13 bool cmp(goods a,goods b)
14 {
15  
16     return  a.xinjia<b.xinjia;
17 }
18  
19  
20 int main()
21 {
22   int m,n,j,f;
23   while(cin>>m)
24   {
25      cin>>n;
26      if(m==-1&&n==-1) break;
27      int i;
28      for(i=0;i<n;i++)
29      {
30        cin>>j>>f;
31        buf[i].J=j;
32        buf[i].F=f;
33        buf[i].xinjia=(double)f/j;
34      }
35      sort(buf,buf+n,cmp);
36       
37      double sum=0.0;
38      for(i=0;i<n;i++)
39      {
40         if(buf[i].F<m)
41         {
42            sum=sum+buf[i].J;
43            m=m-buf[i].F;
44         }
45         else
46         {
47            sum=sum+buf[i].J*(double)m/buf[i].F;
48            break;
49         }
50      }
51  
52      cout<<fixed<<setprecision(3)<<sum<<endl;
53       
54      
55   }
56   return 0;
57 }
58  
59 /**************************************************************
60     Problem: 1433
61     User: 2009declan
62     Language: C++
63     Result: Accepted
64     Time:10 ms
65     Memory:1536 kb
66 ****************************************************************/