LeetCode 589. N叉树的前序遍历

 1 void process(Node* root,vector<int> &ans) {
 2     ans.push_back(root->val);
 3     int n = root->children.size();
 4 
 5     for(int i = 0; i < n; i++)
 6     {
 7         process(root->children[i],ans);
 8     }
 9 }
10 vector<int> preorder(Node* root) {
11     vector<int> ans;
12     if(root)
13         process(root,ans);
14     return ans;
15 }

 1 /*
 2 // Definition for a Node.
 3 class Node {
 4 public:
 5     int val;
 6     vector<Node*> children;
 7 
 8     Node() {}
 9 
10     Node(int _val, vector<Node*> _children) {
11         val = _val;
12         children = _children;
13     }
14 };
15 */
16 class Solution {
17 public:
18     vector<int> preorder(Node* root) {
19         vector<int> ans;
20         if(!root) return ans;
21         stack<Node*> nodeStack;
22         nodeStack.push(root);
23         while(!nodeStack.empty()) {
24             Node* node = nodeStack.top();
25             ans.push_back(node->val);
26             nodeStack.pop();
27             int n = node->children.size();
28             for(int i = n-1; i >= 0 ; i--)
29             {
30                 nodeStack.push(node->children[i]);
31             }
32         }
33         return ans;
34     }
35 };