Binary Tree: Symmetric Binary Tree

Binary Tree: Symmetric Binary 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 isSymmetric(TreeNode* root) {
    
    
        if(root == NULL)
        return true;
        
        return compare(root->left, root->right);
    }
    bool compare(TreeNode *left, TreeNode* right)
    {
    
    
        if(left == NULL && right == NULL)
        return true;
        if(left == NULL || right == NULL)
        return false;     
        if(left->val != right->val)
        return false;
        return compare(left->left, right->right) && compare(left->right, right->left);
    }
};