CDZSC_2015寒假新人（1）——基础 c

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

 

#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
using namespace std;
int main()
{
    int m,n;
    int f[1200],j[1200];
    double a[1200],b[1200];
    int next[1000];
    while((scanf("%d%d",&m,&n)&&(m!=-1||n!=-1)))
    {
        for(int i=0;i<n;i++)
        {
            scanf("%d%d",&f[i],&j[i]);
            a[i]=1.0*f[i]/j[i];
        }
        double num=0;
        for(int i=0;i<n;i++)
        {
            for(int k=i+1;k<n;k++)
            {
                if(a[i]<a[k])
                {
                    swap(a[i],a[k]);
                    swap(f[i],f[k]);
                    swap(j[i],j[k]);
                }
            }
            if(j[i]<m)
            {
                num+=f[i];
                m-=j[i];
            }
            else
            {
                
                num+=1.0*f[i]*m/j[i];
                m=0;
            }
            if(m==0)
            {
                break;
            }
        }
        printf("%.3lf\n",num);
    }
}