101. Symmetric Tree

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {

    public boolean prove(TreeNode node1, TreeNode node2) 
    {

        if (node1 == null && node2 == null) 
        {
            return true;
        }

        if (node1 == null || node2 == null) 
        {
            return false;
        }

        return prove(node1.left, node2.right) && prove(node1.right, node2.left) && node1.val == node2.val;


    }

    public boolean isSymmetric(TreeNode root) 
    {

        if (root == null) 
        {
            return true;
        }

        return prove(root.left, root.right);



        
    }


}