LeetCode@Tree_101_Symmetric Tree

Problem:

Java:

/** * Definition for a binary tree node. * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution { public boolean isSymmetric(TreeNode root)     {    if(root == null)    {    return true;    }return isSymmetric(root.left, root.right);            }        public boolean isSymmetric(TreeNode left, TreeNode right){if (left == null && right == null) return true;if (left == null || right == null) return false;else if (left.val == right.val){return isSymmetric(left.left, right.right) && isSymmetric(left.right, right.left);}return false;}}