두 갈래 나무 관련 문제

Node* FindNextNode(Node* node)
    {
        if (_root == NULL || node == NULL)
            return NULL;
        Node* next = NULL;
        //1、 ， 
        if (node->_right != NULL)
        {
            Node* right = node->_right;
            while (right->_left)
                right = right->_left;
            next = right;
        }
        //2、 , ， ， 
        else
        {
            Node* parent = node->_parent;
            Node* cur = node;
            // parent parent ， 
            while (parent && cur == parent->_right)
            {
                cur = parent;
                parent = parent->_parent;
            }
            next = parent;
        }
        return next;
    }

// 
    Node* FindNextNode(Node* node)
    {
        if (_root == NULL || node == NULL)
            return NULL;
        bool find = false;
        stack s;
        Node* cur = _root;
        while (cur || !s.empty())
        {
            while (cur)
            {   
                s.push(cur);
                cur = cur->_LeftChild;
            }
            Node* top = s.top();
            s.pop();
            if (find)
                return top;
            if (top == node)
                find = true;
            cur = top->_RightChild;
        }
        if (s.empty())
            cout << " " << endl;
        return NULL;
    }

    bool Isbalance()
    {
        int depth = 0;
        return _Isbalance(_root,depth);
    }

// ， 
// ， 。 
    bool _Isbalance(Node*& root, int& depth)
    {
        if (root == NULL)
        {
            depth = 0;
            return true;
        }
        int left = 0;
        int right = 0;
        if (_Isbalance(root->_left, left) && _Isbalance(root->_right, right))
        {
            if (abs(left - right) <= 1)
            {
                depth = (left > right ? left + 1 : right + 1);
                return true;
            }
        }
        return false;
    }