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0101-symmetric-tree.cpp
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32 lines (29 loc) · 860 Bytes
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/*
101. Symmetric Tree
Submitted: December 9, 2024
Runtime: 0 ms (beats 100.00%)
Memory: 18.41 MB (beats 12.19%)
*/
/**
* 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 == nullptr) return true;
return helper(root->left, root->right);
}
bool helper(TreeNode* a, TreeNode* b) {
if (a == nullptr || b == nullptr) return a == b;
if (a->val != b->val) return false;
return helper(a->left, b->right) && helper(a->right, b->left);
}
};