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

Credits:
Special thanks to @mithmatt for adding this problem and creating all test cases.

題目含義：刪除列表中指定的值

1
 
     public ListNode removeElements(ListNode head, int val) {
2         if (head == null) return head;
3         ListNode pointer = head;
4         while (pointer.next != null) {
5             if (pointer.next.val == val) pointer.next = pointer.next.next;
6             else pointer = pointer.next;
7
 
         }
8         return head.val == val ? head.next : head;        
9     }

203. Remove Linked List Elements