LeeCode-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;
* struct ListNode *next;
* };
*/
struct ListNode* removeElements(struct ListNode* head, int val)
{
if(head==NULL)
return NULL;

if(head->next==NULL&&head->val==val)
{
return NULL;
}

if(head->next==NULL&&head->val!=val)
{
return head;
}

struct ListNode *p=head;

while(p->val==val&&p->next!=NULL)
{
p=p->next;
}

if(p->val==val)
{
return NULL;
}

head=p;

if(p->next==NULL)
{
return head;
}

while(p->next->next!=NULL)
{
if(p->next->val==val)
{
p->next=p->next->next;
continue;
}
p=p->next;
}

if(p->next->val==val)
{
p->next=NULL;
}

return head;
}