LeetCode 101. Symmetric Tree

101. Symmetric Tree
My Submissions QuestionEditorial Solution
Total Accepted: 103156 Total Submissions: 305366 Difficulty: Easy
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
Note:
Bonus points if you could solve it both recursively and iteratively.

/** * 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 func(TreeNode *left, TreeNode *right) {        if(left == NULL && right == NULL)            return true;        if(left != NULL && right != NULL && left->val == right->val) {            return func(left->left, right->right) && func(left->right, right->left);        }        return false;    }    bool isSymmetric(TreeNode* root) {        if(root == NULL)            return true;        return func(root->left, root->right);    }};