翻转二叉树或镜像二叉树

TreeNode mirrorTreeNode(TreeNode root){
        if(root == null){
            return null;
        }
        TreeNode left = mirrorTreeNode(root.left);
        TreeNode right = mirrorTreeNode(root.right);
        root.left = right;
        root.right = left;
        return root;
    }

原文地址：https://www.cnblogs.com/yingpu/p/9287194.html