// Runtime: 0 ms, faster than 100.00% of Java online submissions for Flip Equivalent Binary Trees.
class Solution {
    public boolean flipEquiv(TreeNode root1, TreeNode root2) {
        if (root1 == null && root2 == null) return true;
        if ((root1 == null) != (root2 == null)) return false;

        if (root1.val != root2.val) return false;

        TreeNode smallerChild1 = smaller(root1.left, root1.right);
        TreeNode smallerChild2 = smaller(root2.left, root2.right);

        if (!flipEquiv(smallerChild1, smallerChild2)) return false;

        TreeNode biggerChild1 = root1.left == smallerChild1 ? root1.right: root1.left;
        TreeNode biggerChild2 = root2.left == smallerChild2 ? root2.right: root2.left;

        return flipEquiv(biggerChild1, biggerChild2);
    }

    private TreeNode smaller(TreeNode a, TreeNode b) {
        if (a == null || b == null) return null;

        return a.val < b.val ? a: b;
    }
}