【数据结构与算法面试题】二叉树节点的最大距离

void m_length(BSTreeNode *root, int *length, int *max_length){
    if (NULL == root ||
        (NULL == root->m_pLeft && NULL == root->m_pRight)){
        if ((*length) > (*max_length)) (*max_length) = (*length);
        return;
    }
    (*length) ++;
    m_length(root->m_pLeft, length, max_length);
    (*length) --;

    (*length) ++;
    m_length(root->m_pRight, length, max_length);
    (*length) --;
}