Description
For a binary tree T, we can define a flip operation as follows: choose any node, and swap the left and right child subtrees.
A binary tree XΒ is flip equivalent to a binary tree Y if and only if we can make X equal to Y after some number of flip operations.
Given the roots of two binary trees root1
and root2
, return true
if the two trees are flip equivalent or false
otherwise.
Β
Example 1:

Input: root1 = [1,2,3,4,5,6,null,null,null,7,8], root2 = [1,3,2,null,6,4,5,null,null,null,null,8,7] Output: true Explanation: We flipped at nodes with values 1, 3, and 5.
Example 2:
Input: root1 = [], root2 = [] Output: true
Example 3:
Input: root1 = [], root2 = [1] Output: false
Β
Constraints:
- The number of nodes in each tree is in the range
[0, 100]
. - Each tree will have unique node values in the range
[0, 99]
.
Solution
Python3
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, val=0, left=None, right=None):
# self.val = val
# self.left = left
# self.right = right
class Solution:
def flipEquiv(self, root1: Optional[TreeNode], root2: Optional[TreeNode]) -> bool:
def compare(root1, root2):
if not root1 and not root2:
return True
if not root1 or not root2:
return False
if root1.val != root2.val:
return False
if compare(root1.left, root2.left) and compare(root1.right, root2.right):
return True
if compare(root1.left, root2.right) and compare(root1.right, root2.left):
return True
return False
return compare(root1, root2)