How to delete two items in a row in a linked list

Question

void delete_double (LN*& l) {
    if (l == nullptr)
        return;

    LN *p = l;
    while ( p -> next != nullptr && p -> next -&g         


        

Answer 1

Before or after you delete p, the item before p should point to the item after the two deleted items. Otherwise, the link list will broken.

Furthermore, for the while-loop, you may only stop when you arrive the last item. Otherwise, if the last two items are the same, you cannot correctly delete it.

Here is my version. I used a dummy item to point to the item before the current compared item. Notice this cannot deal with 3 items in a row.

void delete_double (LN*& l) {
    if (l == nullptr)
        return;
    LN *dummy = new LN;
    dummy -> next = l;
    while ( dummy -> next != nullptr && dummy -> next -> next != nullptr) // search until the last but two item
    {
        if (dummy -> next -> value == dummy -> next -> next -> value) // the current value is equal to the next value in the linked list
        {
            dummy -> next = dummy -> next -> next -> next;  // link the item after dummy to the item after the deleted items         
        }
        dummy = dummy -> next; // move dummy to the next, notice that this cannot deal with 3 items in a row
    }
    return;
}