【leetcode刷题】T151-N叉树的前序遍历

"""
# Definition for a Node.
class Node(object):
    def __init__(self, val, children):
        self.val = val
        self.children = children
"""
class Solution(object):
    def preorder(self, root):
        """
        :type root: Node
        :rtype: List[int]
        """
        if not root:
            return []
        res = []
        self.helper(root, res)
        return res

    def helper(self, node, res):
        res.append(node.val)
        for child in node.children:
            self.helper(child, res)

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

    Node() {}

    Node(int _val, vector<Node*> _children) {
        val = _val;
        children = _children;
    }
};
*/
class Solution {
public:
    vector<int> preorder(Node* root) {
        vector<int> res;
        if(!root)
            return res;
        helper(root, res);
        return res;
    }

    void helper(Node* node, vector<int>& res){
        res.push_back(node->val);
        for(auto child: node->children)
            helper(child, res);
    }
};