Symmetric Tree

Problem

Given the root of a binary tree, check whether it is a mirror of itself (i.e., symmetric around its center).

Solution Approach

Expected Time complexity: $O(n)$

Click - to see solution code

C++

class Solution {
   public:
    bool traversal(TreeNode* p, TreeNode* q) {
        if (!p && !q) return true;
        if ((!p && q) || (p && !q)) return false;
        if (p->val != q->val) return false;
        return (traversal(p->right, q->left) & traversal(p->left, q->right));
    }

    bool isSymmetric(TreeNode* root) {
        return traversal(root->left, root->right);
    }
};