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;
}