Flip Equivalent Binary Trees

LeetCode Q 951 - 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.
Flipped Trees Diagram

Note:

• Each tree will have at most 100 nodes.
• Each value in each tree will be a unique integer in the range [0, 99].

Solution: DFS

Code:

public boolean flipEquiv(TreeNode root1, TreeNode root2) {
  if (root1 == null && root2 == null) return true;
  if (root1 == null || root2 == null || 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)); 
}