Symmetric Binary Tree.png
解題思路 ：
另外寫一個 function 一次放入兩個點來檢查 ( left and right child ) 裡面除了檢查兩個點的數值是否相同以外 另外 recursive 跑 (左子-> 左子, 右子->右子) 以及 (左子->右子, 右子->左子) 的組合是否都滿足相同的條件 都成立則回傳 true 否則判斷為 false
C++ code :
<pre><code>
/**
- Definition of TreeNode:
- class TreeNode {
- public:
int val;TreeNode *left, *right;TreeNode(int val) {this->val = val;this->left = this->right = NULL;}- }
*/
class Solution {
public:
/**
* @param root, the root of binary tree.
* @return true if it is a mirror of itself, or false.
*/
bool help(TreeNode *left, TreeNode *right)
{
if(left == nullptr && right == nullptr) return true;
if(left == nullptr || right == nullptr) return false;
if(left->val != right->val) return false;
return help(left->left, right->right) && help(left->right, right->left);
}
bool isSymmetric(TreeNode* root) {
// Write your code here
if(root == nullptr) return true;
return help(root->left, root->right);
}
};
