递归求二叉树的度

int TreeDepth(BinaryTreeNode* pRoot)
{
    if(pRoot == NULL)
        return 0;

    int nLeft = TreeDepth(pRoot->m_pLeft);
    int nRight = TreeDepth(pRoot->m_pRight);

    return (nLeft > nRight) ? (nLeft + 1) : (nRight + 1);
}