LeetCode-in-Java
429. N-ary Tree Level Order Traversal
Medium
Given an n-ary tree, return the level order 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).
Example 1:
Input: root = [1,null,3,2,4,null,5,6]
Output: [[1],[3,2,4],[5,6]]
Example 2:
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: [[1],[2,3,4,5],[6,7,8,9,10],[11,12,13],[14]]
Constraints:
- The height of the n-ary tree is less than or equal to
1000 - The total number of nodes is between
[0, 104]
Solution
import com_github_leetcode.Node;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;
/*
// Definition for a Node.
class Node {
public int val;
public List<Node> neighbors;
public Node() {}
public Node(int _val) {
val = _val;
}
public Node(int _val, List<Node> _neighbors) {
val = _val;
neighbors = _neighbors;
}
};
*/
public class Solution {
public List<List<Integer>> levelOrder(Node root) {
List<List<Integer>> result = new ArrayList<>();
if (root == null) {
return result;
}
Queue<Node> queue = new LinkedList<>();
queue.offer(root);
while (!queue.isEmpty()) {
int size = queue.size();
List<Integer> level = new ArrayList<>();
for (int i = 0; i < size; i++) {
Node currentNode = queue.poll();
if (currentNode != null) {
level.add(currentNode.val);
for (Node child : currentNode.neighbors) {
queue.offer(child);
}
}
}
result.add(level);
}
return result;
}
}