代码

unsigned rd()
{
	static unsigned x=471;
	return x=48271ll*x+1;
}
int binary_search(const unsigned *a, int n, unsigned x)
{
	const unsigned *l=a,*r=a+n,*mid;
	while(l+1<r)	(*(mid=l+rd()%(r-l))<=x?l:r)=mid;
	return l-a;
}

评测结果