代码

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

评测结果