刷题-Symmetric Tree 缺python

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).

For example, this binary tree is symmetric:

    1
   / \
  2   2
 / \ / \
3  4 4  3

But the following is not:

    1
   / \
  2   2
   \   \
   3    3

Note:
Bonus points if you could solve it both recursively and iteratively.

confused what "{1,#,2,3}" means? > read more on how binary tree is serialized on OJ.

java：

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public boolean isSymmetric(TreeNode root) {
        if (root == null) return true;
        if (root.left==null && root.right==null) return true;
        return isRight(root.left,root.right);
        
    }
    public boolean isRight(TreeNode n1,TreeNode n2){
        if (n1 == null && n2 == null) return true;
        if (n1 != null && n2 == null) return false;
        if (n1 == null && n2 != null) return false;
        if (n1.val != n2.val) return false;
        return isRight(n1.left,n2.right)&&isRight(n1.right,n2.left);
    }
}