LeetCode58|N叉树的层序遍历

例如，给定一个 3叉树 :返回其层序遍历:

[
     [1],
     [3,2,4],
     [5,6]
]

 
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;

public class LevelNOrderTest {
    public static void main(String[] args) {
        Node node = new Node();
        node.setVal(1);
        List<Node> list = new ArrayList<>();
        Nodew node2 = new Node(3);
        list.add(node2);
        list.add(new Node(2));
        list.add(new Node(4));
        node.setChildren(list);
        List<Node> list1 = new ArrayList<>();
        list1.add(new Node(5));
        list1.add(new Node(6));
        node2.setChildren(list1);
        List<List<Integer>> listList = levelOrder(node);
        System.out.println("listList = " + listList);
    }

    public static List<List<Integer>> levelOrder(Node root) {
        List<List<Integer>> listList = new ArrayList<>();
        if (root == null) {
            return listList;
        }
        Queue<Node> queue = new LinkedList<>();
        queue.add(root);
        while (!queue.isEmpty()) {
            int size = queue.size();
            List<Integer> list = new ArrayList<>();
            for (int i = 0; i < size; i++) {
                Node node = queue.poll();
                list.add(node.val);
                if (node.children != null) {
                    queue.addAll(node.children);
                }
            }
            listList.add(list);
        }
        return listList;
    }
}