# 951. Flip Equivalent Binary Trees 翻转等价二叉树

@TOC

## # 题目描述

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.

Write a function that determines whether two binary trees are flip equivalent. The trees are given by root nodes root1 and root2.

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.
``````

Note:

1. Each tree will have at most 100 nodes.
2. Each value in each tree will be a unique integer in the range [0, 99].

## # 解题方法

### # 递归

``````# 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 flipEquiv(self, root1, root2):
"""
:type root1: TreeNode
:type root2: TreeNode
:rtype: bool
"""
if not root1 and not root2: return True
if not root1 and root2: return False
if root1 and not root2: return False
if root1.val != root2.val: return False
return (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))
``````

## # 日期

2018 年 12 月 2 日 —— 又到了周日