951. Flip Equivalent Binary Trees**

​​https://leetcode.com/problems/flip-equivalent-binary-trees/​​

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:

• Each tree will have at most 100 nodes.
• Each value in each tree will be a unique integer in the range​

  ​[0, 99]​

  ​.

C++ 实现 1

其中

if (!root1 || !root2) return root1 == root2;      

public:
    bool flipEquiv(TreeNode* root1, TreeNode* root2) {
        if (!root1 || !root2) return root1 == root2;
        if (root1->val != root2->val) return false;
        return (flipEquiv(root1->left, root2->left) && flipEquiv(root1->right, root2->right)) ||
            (flipEquiv(root1->left, root2->right) && flipEquiv(root1->right, root2->left));
    }
};