203. Remove Linked List Elements leetcode list

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

ListNode* removeElements(ListNode* head, int val) {
if(NULL == head)
{
return NULL;
}

while(head && head->val==val)
{
head = head->next;
}

if(head == NULL)
{
return NULL;
}

ListNode* p1 = head;
ListNode* p2 = head->next;
ListNode* tmp;

while(p2)
{
if(p2->val == val)
{
while(p2&&p2->val == val)
{
tmp = p2;
p2 = p2->next;
p1->next = p2;
free(tmp);
}
}
else
{
p1 = p1->next;
p2 = p2->next;
}
}

return head;
}