#Leetcode# 951. Flip Equivalent Binary Trees

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

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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.

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Example 1:

Input: root1 = [1,2,3,4,5,6,null,7,8],root2 = [1,8,7] Output: true Explanation: We flipped at nodes with values 1,and 5. 

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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].

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);
    }
};

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