leetcode-Remove Linked List Elements

/**
* 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 *dump=new ListNode(-1);
dump->next=head;
ListNode *p=dump;
ListNode *q=head;
while(q){
bool is_dele=false;
if(q->val==val){
is_dele=true;
while(q->next&&q->val==q->next->val)
q=q->next;
}
if(is_dele)
p->next=q->next;
else
p=p->next;
q=q->next;
}
return dump->next;
}
};