RemoveLinkedListElements203.java

/**
 * Remove all elements from a linked list of integers that have value val.
 * 
 * Example:
 * Input:  1->2->6->3->4->5->6, val = 6
 * Output: 1->2->3->4->5
 */

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */

public class RemoveLinkedListElements203 {
    public ListNode removeElements(ListNode head, int val) {
        ListNode dummy = new ListNode(0);
        dummy.next = head;
        ListNode p = dummy;
        while (p.next != null) {
            if (p.next.val == val) {
                p.next = p.next.next;
            } else {
                p = p.next;
            }
        }
        return dummy.next;
    }

    public ListNode removeElements2(ListNode head, int val) {
        if (head == null) return null;
        head.next = removeElements2(head.next, val);
        return head.val == val ? head.next : head;
    }

}