16.leetcode101_symmetric_tree

Posted 2020-10-23 vlice

1.题目描述

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

判断输入的树杈是否是镜像结构

2.题目分析

判断给出的树杈每一级对应的左节点与右节点是否相同

3.解题思路

从头开始判断下一级的左节点与右节点是否相同

 1 # Definition for a binary tree node.
 2 # class TreeNode(object):
 3 #     def __init__(self, x):
 4 #         self.val = x
 5 #         self.left = None
 6 #         self.right = None
 7 class Solution(object):
 8     def isSymmetric(self, root):
 9         """
10         :type root: TreeNode
11         :rtype: bool
12         """
13         def ismirror(node1,node2):  #自定义函数ismirror判断节点是否对称
14             if node1==None and node2==None: #判断节点结构是否相同
15                 return True
16             elif node1==None or node2==None:
17                 return False
18             else:  #判断数据域是否相同
19                 if node1.val!=node2.val:
20                     return False
21                 else: #节点相同的情况下分析下一级
22                     return ismirror(node1.left,node2.right) and ismirror(node1.right,node2.left)
23         if root==None: #判断是否为空树杈
24             return True
25         else: #不是空树杈的情况下调用自定义的ismirror函数
26             return ismirror(root.left,root.right)

4.解题收获

与leetcode100th题思路相同，通过这两个题进一步加强了对于链表的理解