代码

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

评测结果