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

/**
* Definition for singly-linked list.
* struct ListNode {
*     int val;
*     ListNode *next;
*     ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* removeElements(ListNode* head, int val) {

ListNode node(-1);
node.next=head;
ListNode *pre=&node;
while(head!=NULL)
{
if(head->val==val)
{
pre->next=head->next;
delete head;
head=pre->next;
}
else
{
pre=pre->next;
head=head->next;
}

}
return node.next;
}
};