951. Flip Equivalent Binary Trees

Difficulty: Medium

Related Topics: Tree

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 X 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 equivelent or false otherwise.

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

Example 4:

Input: root1 = [0,null,1], root2 = []
Output: false

Example 5:

Input: root1 = [0,null,1], root2 = [0,1]
Output: true

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

Language: 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: TreeNode, root2: TreeNode) -> bool:
        if not root1 and not root2:
            return True
        elif not root1 and root2:
            return False
        elif root1 and not root2:
            return False
        else:
            return root1.val==root2.val and ((self.flipEquiv(root1.left,root2.right) and self.flipEquiv(root1.right,root2.left)) or (self.flipEquiv(root1.left,root2.left) and self.flipEquiv(root1.right,root2.right)))