/**
* 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:
void search(TreeNode* node, vector<int>& result){
if(!node)
return;
result.push_back(node->val);
search(node->left, result);
search(node->right, result);
}
vector<int> preorderTraversal(TreeNode* root) {
vector<int> result;
search(root, result);
return result;
}
};