Symmetric Tree.cpp

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


/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    bool isSymmetric(TreeNode* root) {
        if (!root) return true;

        queue<TreeNode*> q;
        q.push(root);
        q.push(root);

        while (!q.empty()) {
            TreeNode* t1 = q.front();
            q.pop();
            TreeNode* t2 = q.front();
            q.pop();
            if (t1 == NULL && t2 == NULL) continue;
            if (t1 == NULL || t2 == NULL) return false;
            if (t1->val != t2->val) return false;
            q.push(t1->left);
            q.push(t2->right);
            q.push(t1->right);
            q.push(t2->left);
        }
        return true;
        
    }
};