[LeetCode] 144. Binary Tree Preorder Traversal c++

• 문제

Given the root of a binary tree, return the preorder traversal of its nodes' values.

출처 : https://leetcode.com/problems/binary-tree-preorder-traversal/

Input: root = [1,null,2,3]
Output: [1,2,3]

 

• 문제 해결

class Solution {
private:
    void preorder(TreeNode* curr, vector<int>& vec){
        
        if(!curr){
            return;
        }
        
        vec.push_back(curr->val);
        preorder(curr->left, vec);
        preorder(curr->right, vec);
        
        return;
    }
    
public:
    vector<int> preorderTraversal(TreeNode* root) {
       
        vector<int> vec;
        preorder(root, vec);
        
        return vec;
    }
};