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bt3gl 2023-07-30 21:40:09 -07:00
parent 1d44d182e2
commit a85ed914d3
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42
trees_and_graphs/is_tree_symmetric.py
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#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# author: bt3gl
def is_symmetrical(root: Optional[TreeNode]) -> bool:
stack = [(root, root)]
while stack:
node1, node2 = stack.pop()
if (not node1 and node2) or (not node2 and node1):
return False
elif not node1 and not node2:
continue
elif node1 and node2 and node1.val != node2.val:
return False
stack.append([node1.left, node2.right])
stack.append([node1.right, node2.left])
return True
def is_symmetrical_recursive(root: Optional[TreeNode]) -> bool:
def helper(node1, node2):
if (not node1 and node2) or \
(not node2 and node1) or \
(node1 and node2 and node1.val != node2.val):
return False
if (not node1 and not node2):
return True
return helper(node1.left, node2.right) and helper(node2.left, node1.right)
return helper(root.left, root.right)