LeetCode---Symmetric-Tree

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).

For example, this binary tree is symmetric:

1

/
2 2 / \ /
3 4 4 3 But the following is not: 1 /
2 2 \
3 3

/**

• 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 isSymmetric(TreeNode root) {

   if(root == NULL)
       return true;
   
   return checkSymmetric(root->left, root->right);
  

  }

  bool checkSymmetric(TreeNode* left, TreeNode* right) { if(left == NULL && right == NULL) return true; if(left == NULL || right == NULL) return false;

   return (left->val == right->val) && checkSymmetric(left->left, right->right) && checkSymmetric(right->left, left->right);
  

  } };