struct TreeNode* invertTree(struct TreeNode* root)

{

    if ( NULL == root )

    {

        return NULL;

    }

    if ( NULL == root->left && NULL == root->right )

    {

        //叶子节点

        return root;

    }

    //交换左右子节点

    struct TreeNode * pTreeNodeTmp = root->left;

    root->left = root->right;

    root->right = pTreeNodeTmp;

    invertTree(root->left);

    invertTree(root->right);

    return root;

}