Package g0401_0500.s0430_flatten_a_multilevel_doubly_linked_list

Class Solution

java.lang.Object

g0401_0500.s0430_flatten_a_multilevel_doubly_linked_list.Solution

public class Solution
extends Object

430 - Flatten a Multilevel Doubly Linked List\. Medium You are given a doubly linked list, which contains nodes that have a next pointer, a previous pointer, and an additional **child pointer**. This child pointer may or may not point to a separate doubly linked list, also containing these special nodes. These child lists may have one or more children of their own, and so on, to produce a **multilevel data structure** as shown in the example below. Given the `head` of the first level of the list, **flatten** the list so that all the nodes appear in a single-level, doubly linked list. Let `curr` be a node with a child list. The nodes in the child list should appear **after** `curr` and **before** `curr.next` in the flattened list. Return _the_ `head` _of the flattened list. The nodes in the list must have **all** of their child pointers set to_ `null`. **Example 1:**  **Input:** head = [1,2,3,4,5,6,null,null,null,7,8,9,10,null,null,11,12] **Output:** [1,2,3,7,8,11,12,9,10,4,5,6] **Explanation:** The multilevel linked list in the input is shown. After flattening the multilevel linked list it becomes:  **Example 2:**  **Input:** head = [1,2,null,3] **Output:** [1,3,2] **Explanation:** The multilevel linked list in the input is shown. After flattening the multilevel linked list it becomes:  **Example 3:** **Input:** head = [] **Output:** [] **Explanation:** There could be empty list in the input. **Constraints:** * The number of Nodes will not exceed `1000`. * 1 <= Node.val <= 105 **How the multilevel linked list is represented in test cases:** We use the multilevel linked list from **Example 1** above: 1---2---3---4---5---6--NULL | 7---8---9---10--NULL | 11--12--NULL The serialization of each level is as follows: [1,2,3,4,5,6,null] [7,8,9,10,null] [11,12,null] To serialize all levels together, we will add nulls in each level to signify no node connects to the upper node of the previous level. The serialization becomes: [1, 2, 3, 4, 5, 6, null] | [null, null, 7, 8, 9, 10, null] | [ null, 11, 12, null] Merging the serialization of each level and removing trailing nulls we obtain: [1,2,3,4,5,6,null,null,null,7,8,9,10,null,null,11,12]

Constructor Summary

Constructors

Constructor	Description
Solution()

Method Summary

Modifier and Type	Method	Description
Node	flatten(Node head)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

Solution

public Solution()

Method Details

flatten

public Node flatten(Node head)