面试题52：缺少i的乘积数组

vector<int> multiply(const vector<int>& A) {
    int len = A.size();
    vector<int> result(len, 1);
    result[0] = 1;
    for (int i = 1; i < len; i++)
    {
        result[i] = result[i - 1] * A[i - 1];    //result[i]保存下三角
    }
    int tmp = 1;
    for (int i = len - 2; i >= 0; i--)
    {
        tmp = tmp * A[i + 1];    //tmp保存上三角
        result[i] *= tmp;
    }
    return result;
}