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double linked list

zachtastic (12)
im trying to create a doublely linked list of objects and am having trouble getting it to actually insert the data. the program runs but seg faults every time it trys to insert the second item into the list. all the main program is doing is sending the methods the item data so that i can be put in the list. ive tracked down the error to one of these two methods.

thnaks for the help

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ListNode *List::find(int index) const
{
   if ( (index < 1) || (index > getLength()) )
      return NULL;

   else  // count from the beginning of the list.
   {  if (index < size /2)
      {
       ListNode *cur = head;
       ListNode *previous = NULL;
      for (int skip = 1; skip < index; ++skip)
         cur = cur->next;
       previous = cur -> prev;
      return cur;
      }
      else
      {
          ListNode *cur = tail;
          ListNode *previous = NULL;
          for (int skip = 1; skip < index; --skip)
            cur = cur -> prev;
            previous = cur -> prev;
      }
      }  // end if

void List::insert(int index, const ListItemType& newItem)
   throw(ListIndexOutOfRangeException, ListException)
{
   int newLength = getLength() + 1;
   if ( (index < 1) || (index > newLength) )
      throw ListIndexOutOfRangeException(
	 "ListIndexOutOfRangeException: insert index out of range");
   else
   {  // try to create new node and place newItem in it
      try
      {
	 ListNode *newPtr = new ListNode;
	 size = newLength;
	 newPtr->item = newItem;

	 // attach new node to list
	 if (index == 1)
	 {  // insert new node at beginning of list
	    newPtr->next = head;
	    head = newPtr;
            newPtr ->prev = NULL;
            newPtr ->item = newItem;

	 }
	 else
	 {  ListNode *previous = find(index-1);
            ListNode * after = find(index + 1);
            // insert new node after node
            // to which prev points
            newPtr->next = previous -> next;
            previous -> next = newPtr;
            after -> prev = newPtr;
            newPtr -> prev = previous;
	 }  // end if
      }  // end try
      catch (bad_alloc e)
      {
	 throw ListException(
	    "ListException: memory allocation failed on insert");
      }  // end catch
   }  // end if
}  // end insert


vijaysaluru (23)
just check n verify the code in bold:

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       if (index < size /2)
      {
       ListNode *cur = head;
       ListNode *previous = NULL;
      for (int skip = 1; skip < index; ++skip)
         cur = cur->next;
       previous = cur -> prev;
      return cur;
      }
      else
      {
          ListNode *cur = tail;
          ListNode *previous = NULL;
          for (int skip = 1; skip < index; --skip)
            cur = cur -> prev;
            previous = cur -> prev;
      }

It should be for (int skip = size; skip < index; --skip)
bluecoder (763)
also you are missing on of the closing braces of the find function. please check .
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