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  • [LC] 429. N-ary Tree Level Order Traversal

    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]]

    /*
    // Definition for a Node.
    class Node {
        public int val;
        public List<Node> children;
    
        public Node() {}
    
        public Node(int _val) {
            val = _val;
        }
    
        public Node(int _val, List<Node> _children) {
            val = _val;
            children = _children;
        }
    };
    */
    class Solution {
        public List<List<Integer>> levelOrder(Node root) {
            List<List<Integer>> res = new ArrayList<>();
            if (root == null) {
                return res;
            }
            Queue<Node> queue = new LinkedList<>();
            queue.offer(root);
            while (!queue.isEmpty()) {
                int size = queue.size();
                List<Integer> list = new ArrayList<>();
                for (int i = 0; i < size; i++) {
                    Node cur = queue.poll();
                    list.add(cur.val);
                    for (Node node: cur.children) {
                        if (node != null) {
                            queue.offer(node);
                        }
                    }
                }
                res.add(list);         
            }
            return res;
        }
    }
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  • 原文地址:https://www.cnblogs.com/xuanlu/p/12148716.html
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