> #include "stdio.h"
> #include "stdlib.h"
> #include "math.h"
> struct song{
>     int  id;
>     int  ln;
>     double fr;
> }a[1<<16];
> int cmp(const void *p1,const void *p2)
> {
>     if( (*(struct song *)p2).fr>(*(struct song *)p1).fr   ) 
>         return 1;
>     if( fabs((*(struct song *)p2).fr==(*(struct song *)p1).fr)<0.000001  )  
                                      ~~这个等号比较诡异
>         return 0;
>     return -1;      
>          
> }
> int  main()
> {
>     int  i,n,num;
>     scanf("%d",&n);
>     for(i=0;i<n;i++) 
>     {
>         scanf("%d %d %lf",&a[i].id,&a[i].ln,&a[i].fr);
>         a[i].fr/=a[i].ln;
>     }
>     scanf("%d",&num);
>     qsort(a,n,sizeof(struct song),cmp);
>     printf("%d\n",a[num-1].id);
> }