代码

int binary_search(unsigned *a, unsigned n, register unsigned x)
{
	register unsigned l=0,r=n-1,mid;
	do
	{
		mid=(l+r)>>1;
		(a[mid]<x)?(l=mid+1):(r=mid);
	}
	while(l!=r);
	return l;
}

评测结果