LeetCode - 590. N-ary Tree Postorder Traversal

590. N-ary Tree Postorder Traversal - easy

문제

Given an n-ary tree, return the postorder traversal of its nodes’ values.

Nary-Tree input serialization is represented in their level order traversal, each group of children is separated by the null value (See examples).

제한사항

• The height of the n-ary tree is less than or equal to 1000
• The total number of nodes is between [0, 10^4]

입출력 예

Input: root = [1,null,3,2,4,null,5,6]
Output: [5,6,3,2,4,1]

Input: root = [1,null,2,3,4,5,null,null,6,7,null,8,null,9,10,null,null,11,null,12,null,13,null,null,14]
Output: [2,6,14,11,7,3,12,8,4,13,9,10,5,1]

풀이

• Tree

/*
// Definition for a Node.
class Node {
public:
    int val;
    vector<Node*> children;

    Node() {}

    Node(int _val) {
        val = _val;
    }

    Node(int _val, vector<Node*> _children) {
        val = _val;
        children = _children;
    }
};
*/
class Solution {
public:
    vector<int> postorder(Node* root) {
        if(root == nullptr)
            return {};
        
        vector<int> item;

        for(auto i = 0 ; i < root->children.size() ; ++i){
            // 재귀로 Tree PostOrder 구현
            auto temp = postorder(root->children[i]);
            
    	    // 재귀적으로 PreOrder로 조회한 자식노드들을 현재 vector에 뒤에 붙임
            item.insert(item.end(), temp.begin(), temp.end());            
        }
        
        // 자식 노드를 모두 조회한 후, 현재 노드 조회
        item.push_back(root->val);
        
        return item;
    }
};