题目描述
请实现一个函数,用来判断一颗二叉树是不是对称的。注意,如果一个二叉树同此二叉树的镜像是同样的,定义其为对称的。
1
/ \
2 2
/ \ / \
3 4 4 3
思路:
- 根节点为空的二叉树也是对称二叉树
- self.isSymBT(tree1.left,tree2.right) and self.isSymBT(tree1.right,tree2.left)
python代码:
# -*- coding:utf-8 -*-
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution:
def isSymmetrical(self, pRoot):
# write code here
if not pRoot:
return True
return self.isSymBT(pRoot.left,pRoot.right)
def isSymBT(self,tree1,tree2):
if tree1 == None and tree2 == None:
return True
if tree1 == None or tree2 == None:
return False
if tree1.val != tree2.val:
return False
else:
return self.isSymBT(tree1.left,tree2.right) and self.isSymBT(tree1.right,tree2.left)