代码

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

评测结果