求二叉树中节点的最大距离

class BTree
{
public:
    struct Node
    {
        int _val;        
        Node * _lChild;
        Node * _rChild;    
        Node * _pParent;
    };
        int MaxLength();
        int MaxLength(BTree::Node * node, int & maxLen);
}

int BTree::MaxLength()
{
    int maxLen =0;
    MaxLength(_pRoot,maxLen);
    return maxLen;
}

int BTree::MaxLength(BTree::Node * node, int & maxLen)
{
    if(node==0)
        return 0;
    int l = Height(node->_lChild);
    int r = Height(node->_rChild);
    if(maxLen<(l+r))
        maxLen = l+r;
    return 1 + max(l,r);
}