代码

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

评测结果