代码

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

评测结果