LeetCode 203 - Remove Linked List Elements

http://www.programcreek.com/2014/04/leetcode-remove-linked-list-elements-java/

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

Example

Given: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6
Return: 1 --> 2 --> 3 --> 4 --> 5

The key to solve this problem is using a helper node to track the head of the list.
http://www.jiuzhang.com/solutions/remove-linked-list-elements/
http://www.programcreek.com/2014/04/leetcode-remove-linked-list-elements-java/

    public ListNode removeElements(ListNode head, int val) {
        ListNode dummy = new ListNode(0);
        dummy.next = head;
        head = dummy;
        
        while (head.next != null) {
            if (head.next.val == val) {
                head.next = head.next.next;
            } else {
                head = head.next;
            }
        }
        
        return dummy.next;
    }

https://leetcode.com/discuss/33142/iterative-short-java-solution

public ListNode removeElements(ListNode head, int val) { while (head != null && head.val == val) head = head.next; ListNode curr = head; while (curr != null && curr.next != null) if (curr.next.val == val) curr.next = curr.next.next; else curr = curr.next; return head; }

X. Recursive Version

https://leetcode.com/discuss/33043/3-line-recursive-solution

public ListNode removeElements(ListNode head, int val) { if (head == null) return null; head.next = removeElements(head.next, val); return head.val == val ? head.next : head; }

public ListNode removeElements(ListNode head, int val) { if(head == null) return null; ListNode next = removeElements(head.next, val); if(head.val == val) return next; head.next = next; return head; }

http://www.sigmainfy.com/blog/leetcode-remove-linked-list-elements-iterative-vs-recursive.html

    public ListNode removeElements(ListNode head, int val) {
 if (head == null) {
  return null;
 }

 if (head.val == val){
  head =
                removeElements(head.next, val);
 } else {
  head.next =
                removeElements(head.next, val);
 }

 return head;
    }