代码

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

评测结果