-
Notifications
You must be signed in to change notification settings - Fork 0
/
NaryTreePreorderTraversal.java
55 lines (49 loc) · 1.57 KB
/
NaryTreePreorderTraversal.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
import java.util.*;
/*
* https://leetcode.com/problems/n-ary-tree-preorder-traversal/
*/
public class NaryTreePreorderTraversal {
public List<Integer> preorder(Node root) {
if (root == null) {
return Collections.emptyList();
}
List<Integer> ans = new LinkedList<>();
ans.add(root.value);
Optional.ofNullable(root.children)
.orElse(Collections.emptyList())
.stream()
.map(this::preorder)
.forEach(ans::addAll);
return ans;
}
public static void main(String[] args) {
System.out.println(new NaryTreePreorderTraversal().preorder(
new Node(
1,
Arrays.asList(
new Node(
3,
Arrays.asList(
new Node(5),
new Node(6)
)
),
new Node(2),
new Node(4)
)
)
)); // [1, 3, 5, 6, 2, 4]
}
static class Node {
public int value;
public List<Node> children;
public Node() {}
public Node(int value) {
this(value, null);
}
public Node(int value, List<Node> children) {
this.value = value;
this.children = children;
}
}
}