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101.Symmetric-Tree.py
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38 lines (30 loc) · 879 Bytes
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# https://leetcode.com/problems/symmetric-tree/
#
# algorithms
# Easy (42.17%)
# Total Accepted: 331,989
# Total Submissions: 788,072
# 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
"""
if not root:
return True
return self._is_equal(root.left, root.right)
def _is_equal(self, a, b):
if not a and not b:
return True
elif not a or not b:
return False
elif a.val != b.val:
return False
return self._is_equal(a.left, b.right) and \
self._is_equal(a.right, b.left)