g0701_0800.s0707_design_linked_list

Class MyLinkedList

java.lang.Object

g0701_0800.s0707_design_linked_list.MyLinkedList

public class MyLinkedList
extends Object

707 - Design Linked List.

Medium

Design your implementation of the linked list. You can choose to use a singly or doubly linked list.
A node in a singly linked list should have two attributes: val and next. val is the value of the current node, and next is a pointer/reference to the next node.
If you want to use the doubly linked list, you will need one more attribute prev to indicate the previous node in the linked list. Assume all nodes in the linked list are 0-indexed.

Implement the MyLinkedList class:

• MyLinkedList() Initializes the MyLinkedList object.
• int get(int index) Get the value of the indexth node in the linked list. If the index is invalid, return -1.
• void addAtHead(int val) Add a node of value val before the first element of the linked list. After the insertion, the new node will be the first node of the linked list.
• void addAtTail(int val) Append a node of value val as the last element of the linked list.
• void addAtIndex(int index, int val) Add a node of value val before the indexth node in the linked list. If index equals the length of the linked list, the node will be appended to the end of the linked list. If index is greater than the length, the node will not be inserted.
• void deleteAtIndex(int index) Delete the indexth node in the linked list, if the index is valid.

Example 1:

Input

[“MyLinkedList”, “addAtHead”, “addAtTail”, “addAtIndex”, “get”, “deleteAtIndex”, “get”]

[1], [3], [1, 2], [1], [1], [1

Output: [null, null, null, null, 2, null, 3]

Explanation:

MyLinkedList myLinkedList = new MyLinkedList(); 
myLinkedList.addAtHead(1); 
myLinkedList.addAtTail(3); 
myLinkedList.addAtIndex(1, 2); // linked list becomes 1->2->3 
myLinkedList.get(1); // return 2 
myLinkedList.deleteAtIndex(1); // now the linked list is 1->3 
myLinkedList.get(1); // return 3

Constraints:

• 0 <= index, val <= 1000
• Please do not use the built-in LinkedList library.
• At most 2000 calls will be made to get, addAtHead, addAtTail, addAtIndex and deleteAtIndex.

Constructor Summary

Constructors

Constructor and Description
MyLinkedList()

Method Summary

Modifier and Type	Method and Description
void	addAtHead(int val)
void	addAtIndex(int index, int val)
void	addAtTail(int val)
void	deleteAtIndex(int index)
int	get(int index)

Methods inherited from class java.lang.Object

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

Constructor Detail

MyLinkedList

public MyLinkedList()

Method Detail

get

public int get(int index)

addAtHead

public void addAtHead(int val)

addAtTail

public void addAtTail(int val)

addAtIndex

public void addAtIndex(int index,
                       int val)

deleteAtIndex

public void deleteAtIndex(int index)