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* h = head;
ListNode* pre = NULL;
while(h!=NULL)//顺序查找，O(N)
{
if(h->val == val)
{
if(pre == NULL)
{
head = head->next;
pre = NULL;
}
else
{
pre->next = h->next;
}
}
else
{
pre = h;
}
h = h->next;
}
return head;
}
};