delete the duplicate values from the single linked list only function

SinglyLinkedListNode* removeDuplicates(SinglyLinkedListNode* head) {
    SinglyLinkedListNode *p, *q,*temp;
    if(head==NULL)
        return NULL;
    if(head->next== NULL)
        return head;
    p=head;
    while(head->next!=NULL)
    {
        if(head->data==head->next->data)
        {
            head->next=head->next->next;
        }
        else
        {
            head=head->next;
        }
    }
    return p;
}