101.对称二叉树.py

#
# @lc app=leetcode.cn id=101 lang=python
#
# [101] 对称二叉树
#
# https://leetcode-cn.com/problems/symmetric-tree/description/
#
# algorithms
# Easy (48.79%)
# Likes:    473
# Dislikes: 0
# Total Accepted:    63.3K
# Total Submissions: 129.8K
# Testcase Example:  '[1,2,2,3,4,4,3]'
#
# 给定一个二叉树，检查它是否是镜像对称的。
# 
# 例如，二叉树 [1,2,2,3,4,4,3] 是对称的。
# 
# ⁠   1
# ⁠  / \
# ⁠ 2   2
# ⁠/ \ / \
# 3  4 4  3
# 
# 
# 但是下面这个 [1,2,2,null,3,null,3] 则不是镜像对称的:
# 
# ⁠   1
# ⁠  / \
# ⁠ 2   2
# ⁠  \   \
# ⁠  3    3
# 
# 
# 说明:
# 
# 如果你可以运用递归和迭代两种方法解决这个问题，会很加分。
# 
#

# @lc code=start
# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def isSymmetric(self, root):
        """
        :type root: TreeNode
        :rtype: bool
        """
        return self.compare(root,root)

    def compare(self,root1,root2):
        if root1==None and root2==None:
            return True
        elif root1!=None and root2!=None and root1.val==root2.val:
            return self.compare(root1.left,root2.right) and self.compare(root1.right,root2.left)
        else:
            return False



        
# @lc code=end