951. Flip Equivalent Binary Trees 

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

        if (root1 != null && root2 != null) {
            if (root1.val != root2.val) {
                return false;
            } else {
                return (flipEquiv(root1.left, root2.left) && flipEquiv(root1.right, root2.right)) ||
                        (flipEquiv(root1.left, root2.right) && flipEquiv(root1.right, root2.left));
            }
        } else {
            return false;
        }
    }
}

References

951. Flip Equivalent Binary Trees