代码

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

评测结果