LeetCode101_对称二叉树

1. 题目

2. 题解

# 101
class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right


class Solution:
    def isSymmetric(self, root: TreeNode) -> bool:
        if root is None:
            return True
        left = root.left
        right = root.right
        return self.is_equal(left, right)

    def is_equal(self, left: TreeNode, right: TreeNode) -> bool:
        if left is None and right is not None:
            return False
        if left is not None and right is None:
            return False
        if left is None and right is None:
            return True
        else:
            return left.val == right.val and self.is_equal(left.left, right.right) and self.is_equal(left.right, right.left)