https://leetcode.com/problems/flip-equivalent-binary-trees/
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
100nodes. - Each value in each tree will be a unique integer in the range
[0, 99].
代码：
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
bool flipEquiv(TreeNode* root1, TreeNode* root2) {
if(!root1 && !root2) return true;
if(!root1 || !root2) return false;
if(root1 -> val != root2 -> val) return false;
return flipEquiv(root1 -> left, root2 -> right) && flipEquiv(root1 -> right, root2 -> left) ||
flipEquiv(root1 -> left, root2 -> left) && flipEquiv(root1 -> right, root2 -> right);
}
};
为什么要 
这个判断