[Leetcode]Symmetric Tree

/**

 * Definition for binary tree

 * struct TreeNode {

 *     int val;

 *     TreeNode *left;

 *     TreeNode *right;

 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}

 * };

 */

class Solution {

public:

    bool isSymmetric(TreeNode *root) {

        if (root==NULL)return true;

        else if(root->left==NULL&&root->right==NULL)return true;

        else return isNodeSymmetric(root->left,root->right);

    }

    bool isNodeSymmetric(TreeNode *left,TreeNode *right)

    {

        if(left==NULL&&right==NULL)return true;

        if((left == NULL && right != NULL) || (left != NULL && right == NULL) ) return false;

        else if(left->val!=right->val)return false;

        else return isNodeSymmetric(left->left,right->right)&& isNodeSymmetric(left->right,right->left);

        

    }

          

};