代码

int binary_search(const unsigned *a, int n, unsigned x)
{
	int l=1;n--;while(l<=n){
        int mid=(l+n)/2;
        if(a[mid]>x)
          n=mid-1;
        else if(a[mid]<x)
          l=mid+1;
        else return mid;
        }
        return 0;
}

评测结果