> /* Poj 1064, wrote by Dream Chen 2010/12/12*/
> #include <iostream>
> #include <string>
> using namespace std;
> 
> int N = 0;
> int K = 0;
> int l = 0;
> int r = 0;
> int mid = 0;
> int a[11000];
> int res = 0;
> bool judge(int t);
> int main(void)
> {
> 	memset((void*)a,0,sizeof(a));
> 	while(EOF != scanf("%d %d",&N,&K))
> 	{
> 
> 		for (int i = 0; i < N; ++i)
> 		{
> 			double tmp = 0;
> 			scanf("%lf",&tmp);
> 			a[i] = (int)(tmp*100);
> 			if (a[i] > r) 
> 			{
> 				r = a[i];
> 			}
> 		}  
> 		while(l <= r) 
> 		{
> 			mid = (l + r) / 2;
> 			// suit the requiment
> 			if (judge(mid))
> 			{
> 				l = mid + 1; 
> 			}
> 			else
> 			{
> 				r = mid - 1;
> 			}
> 		}
> 
> 		printf("%.2lf\n",r*0.01);
> 	}
> 		return 0;
> }
> 
> bool judge(int t)
> {
> 	int sum = 0;
> 	for (int i = 0; i < N; ++i)
> 	{
> 		sum += a[i] / t;
> 	}
> 	if (sum >= K)
> 	{
> 		return true;
> 	}
> 	else
> 	{
> 		return false;
> 	}
> }

原来是这里错了，在judge(int t)这个函数里面，有可能传了个0进去，
汗！！！