LeetCode 101. 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
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);
    }
};

/**

* 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);

}

};

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