Symmetric Tree

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
   bool iss(TreeNode* root_left,TreeNode *root_right){
        if(root_left==NULL) return root_right==NULL;
        if(root_right==NULL) return root_left==NULL;
        if(root_left->left == NULL && root_left->right == NULL){ 
                    if(root_right->left == NULL && root_right->right == NULL) 
                        return root_left->val == root_right->val;
                        return false;
        }
        if(!iss(root_left->left,root_right->right)) return false;
        if(!iss(root_right->left,root_left->right)) return false;
        if(root_left->val != root_right->val) return false;
        return true;
    }
  bool isSymmetric(TreeNode* root) {
        if(root==NULL) return true;
        if(root->left == NULL && root->right == NULL) return true;
        return iss(root->left,root->right);
    }
 
};