@@ -6,47 +6,33 @@ class Node {
66
77 public Node() {}
88
9- public Node(int _val,List<Node> _children) {
9+ public Node(int _val) {
10+ val = _val;
11+ }
12+
13+ public Node(int _val, List<Node> _children) {
1014 val = _val;
1115 children = _children;
1216 }
1317};
1418*/
15- class Solution {
16- List <Integer >values =new ArrayList <>();
17- public List <Integer >preorder (Node root ) {
18- updateListIterative (root );
19- return values ;
20- }
21-
22- private void updateListIterative (Node root ) {
23- if (root ==null ) {
24- return ;
25- }
26-
27- Stack <Node >stack =new Stack <>();
28- stack .push (root );
2919
30- while (!stack .empty ()) {
31- Node temp =stack .pop ();
32- values .add (temp .val );
33-
34- List <Node >childrens =temp .children ;
35-
36- for (int i =childrens .size ()-1 ;i >=0 ;i --) {
37- stack .push (childrens .get (i ));
38- }
39- }
20+ class Solution {
21+ public List <Integer >preorder (Node root ) {
22+ if (root ==null ) {
23+ return new ArrayList <>();
4024 }
41-
42- private void updateListRecursive ( Node root ) {
43- if root == null ) {
44- return ;
45- }
46-
47- values . add ( root . val ) ;
48- for (Node node : root . children ) {
49- updateListRecursive ( node );
50-
25+ List < Integer > list = new ArrayList <>();
26+ Stack < Node > stack = new Stack <>();
27+ stack . push (root );
28+ while (! stack . isEmpty ()) {
29+ Node popped = stack . pop ();
30+ list . add ( popped . val );
31+ List < Node > children = popped . children ;
32+ for (int i = children . size () - 1 ; i >= 0 ; i -- ) {
33+ stack . push ( children . get ( i ) );
34+ }
5135 }
36+ return list ;
37+ }
5238}