Insert a new element at a specific index in the given linked list. The index is 0 based, and if the index is out of the list's scope, you do not need to do anything.
Examples:
1 -> 2 -> 3 -> null, insert 4 at index 3, --> 1 -> 2 -> 3 -> 4 -> null
1 -> 2 -> null, insert 4 at index 0, --> 4 -> 1 -> 2 -> null
1 public class Solution {
2 public ListNode insert(ListNode head, int index, int value) {
3 // Write your solution here
4 if (head == null || index < 0) {
5 return head;
6 }
7 int length = getLength(head) ;
8 //corner case: index out of list's scope
9 if (length < index) {
10 return head ;
11 }
12 ListNode dummy = new ListNode(0);
13 ListNode curr = dummy ;
14 dummy.next = head ;
15 int counter = 0 ;
16 /*
17 1 -> 2 -> 3-> null insert @ index = 1
18 d/c-->
19 c
20 */
21 while(curr != null ){
22 if (counter == index) {
23 ListNode newNode = new ListNode(value);
24 ListNode temp = curr.next ;
25 curr.next = newNode ;
26 newNode.next = temp ;
27 break ;
28 }
29 curr = curr.next ;
30 counter++;
31 }
32 return dummy.next ;
33 }
34
35 private int getLength(ListNode head){
36 if (head == null) {
37 return 0;
38 }
39 ListNode curr = head ;
40 int res = 0 ;
41 while(curr != null){
42 curr = curr.next ;
43 res++;
44 }
45 return res ;
46 }
47
48 }