// Time:  O(n)
// Space: O(h)

/**
 * 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 || 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));
    }
};