FatMouse' Trade

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)

Total Submission(s): 92544    Accepted Submission(s): 32114

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

 

 

解题思路：贪心，开一个结构体后按照平均值从大到小排序，先换掉平均值大的房间里的JavaBean，输出用printf输出，用setpricision会wa，原因在于setprecision会四舍五入丢失精度。

#include
       
        #include
        
         using namespace std;struct jb{    double j,f,avg;};bool cmp(jb x,jb y){    return x.avg
         
          >n>>m&&n!=-1)    {        jb s[1001];        for(int i=0;i
          
           >s[i].j>>s[i].f;s[i].avg=s[i].j/s[i].f;}        sort(s,s+m,cmp);        double sum=0;        for(int i=m-1;i>=0;--i)        {            if(n>=s[i].f)            {                n-=s[i].f;                sum+=s[i].j;            }            else if(n
           
            0)            {                sum+=s[i].avg*n;                break;            }        }        printf("%.3lf\n",sum);        //cout<
            
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