Remove Linked List Elements

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

从链表中删除节点为给定值得所有节点。对于在链表中删除节点的问题，如果头结点可能被删除的情况下，我们往往创建一个helper节点，让它指向头结点。这样从helper节点的next开始处理，最后返回help.next就可以了。代码如下：

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode removeElements(ListNode head, int val) {
        ListNode helper = new ListNode(0);
        helper.next = head;
        head = helper;
        while(head.next != null) {
            if(head.next.val == val) {
                head.next = head.next.next;
            } else {
                head = head.next;
            }
        }
        return helper.next;
    }
}