leetcode讲解--429. N-ary Tree Level Order Traversal

题目Given an n-ary tree, return the level order traversal of its nodes’ values. (ie, from left to right, level by level).For example, given a 3-ary tree:We should return its level order traversal:[ [1], [3,2,4], [5,6]]Note:The depth of the tree is at most 1000.The total number of nodes is at most 5000.[题目地址]https://leetcode.com/problems…讲解这道题我真的想了有很久，刚开始想用队列，但是发现不知道怎么分割每一层，于是就想还是用递归。后来越发想不明白，最后看了别人的解法。其实分割每一层是可以做到的。以后要多练习。java代码/// Definition for a Node.class Node { public int val; public List<Node> children; public Node() {} public Node(int _val,List<Node> _children) { val = _val; children = _children; }};/class Solution { List<List<Integer>> result = new ArrayList<List<Integer>>(); public List<List<Integer>> levelOrder(Node root) { if(root==null){ return result; } Queue<Node> queue = new LinkedList<>(); queue.offer(root); int children_num = 1; List<Integer> rootList = new ArrayList<Integer>(); rootList.add(root.val); result.add(rootList); while(!queue.isEmpty()){ List<Integer> list = new ArrayList<>(); int count=0; for(int i=0;i<children_num;i++){ Node now = queue.poll(); if(now.children!=null){ for(Node node:now.children){ queue.offer(node); list.add(node.val); count++; } } } children_num = count; if(list.size()>0){ result.add(list); } } return result; }}