代码

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

评测结果