[LeetCode] Symmetric

public class Solution {
    public boolean isSymmetric(TreeNode root) {
        if(root == null) return true;
        
        return isTwoTreeSymmetric(root.left, root.right);
    }
    
    public boolean isTwoTreeSymmetric(TreeNode node1, TreeNode node2) {
        if (node1 == null && node2 == null) return true;
        if (node1 == null || node2 == null) return false;
        
        if (node1.val != node2.val) return false;
        
        return isTwoTreeSymmetric(node1.left, node2.right) && isTwoTreeSymmetric(node1.right, node2.left);
    }
}