Remove Linked List Elements

Remove all elements from a linked list of integers that have value val.

Example:

1
2
Input:  1->2->6->3->4->5->6, val = 6
Output: 1->2->3->4->5

Solution:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode removeElements(ListNode head, int val) {
        if (head == null) {
            return head;
        }
        while (head != null && head.val == val) {
            head = head.next;
        }

        ListNode node = head;
        ListNode prev = null;

        while (node != null) {
            if (node.val == val) {
                prev.next = node.next;  
            } else {
                prev = node; 
            }
            node = node.next;
        }
        return head;
    }
}