text: //
  //  Symmetric_Tree.c
  //  MyLeetCode
  //
  //  Created by poco on 2019/2/11.
  //  Copyright © 2019 zyy. All rights reserved.
  //
  
  bool cmp(struct TreeNode* left, struct TreeNode* right)
  {
      
      if(left == NULL && right == NULL)
      {
          return true;
      }
      
      if((left != NULL && right == NULL) || (left == NULL && right != NULL))
      {
          return false;
      }
      
      
      if(left->val == right->val)
      {
          return cmp(left->left, right->right) && cmp(right->left, left->right);;
      }
      else
      {
          return false;
      }
      
  }
  
  
  bool isSymmetric(struct TreeNode* root) {
      
      if(root == NULL)
      {
          return true;
      }
      
      return cmp(root->left, root->right);
      
  }
  