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 equivalent 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
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].
Solutions
Solution 1
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# 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 = rightclassSolution:defflipEquiv(self,root1:Optional[TreeNode],root2:Optional[TreeNode])->bool:defdfs(root1,root2):ifroot1==root2or(root1isNoneandroot2isNone):returnTrueifroot1isNoneorroot2isNoneorroot1.val!=root2.val:returnFalsereturn(dfs(root1.left,root2.left)anddfs(root1.right,root2.right))or(dfs(root1.left,root2.right)anddfs(root1.right,root2.left))returndfs(root1,root2)
/** * Definition for a binary tree node. * type TreeNode struct { * Val int * Left *TreeNode * Right *TreeNode * } */funcflipEquiv(root1*TreeNode,root2*TreeNode)bool{vardfsfunc(root1,root2*TreeNode)booldfs=func(root1,root2*TreeNode)bool{ifroot1==root2||(root1==nil&&root2==nil){returntrue}ifroot1==nil||root2==nil||root1.Val!=root2.Val{returnfalse}return(dfs(root1.Left,root2.Left)&&dfs(root1.Right,root2.Right))||(dfs(root1.Left,root2.Right)&&dfs(root1.Right,root2.Left))}returndfs(root1,root2)}