Set Class - Insert Function

[boydale1]

I am working on a set class and I have successfully written an insert function, but I need the function to insert in an ordered fashion.

bool Set::insert( const EType & A )
{
   bool Flag = false;
   unsigned Position = 0;
   Node * Prev = Head;
   Node * Curr = Head->Succ;
   Node * Temp;

   Temp = new Node;
   if (Temp != NULL )
   {
      Temp->Item = A;
      Temp->Succ = Curr;
      Prev->Succ = Temp;
      Num++;
      Flag = true;
   }
   return Flag;
}

Set::Set()
{
   Num = 0;
   Head = new (nothrow) Node;
   Head->Succ = NULL;
}

class Set
{
  private:

    struct Node
    {
      EType Item;     // User data item
      Node * Succ;    // Link to the node's successor
    };

    unsigned Num;     // Number of user data items in the set
    Node * Head;      // Link to the head of the chain

Tell me if anything else is needed

[Clockowl]

Scan the set until you find a value higher or lower (depends on how you sort) then the current value, insert it there?

[boydale1]

I tried doing that several separate times, but i cannot avoid a segmentation fault.

bool Set::insert( const EType & A )
{
   bool Flag = false;
   unsigned Position = 0;
   Node * Prev = Head;
   Node * Curr = Head->Succ;

   while ( (Curr->Item < A) and (Curr->Succ != NULL) )
   {
      Prev = Curr;
      Curr = Curr->Succ;
      cout << Curr->Item;
   }

   if ( (Curr->Item != A) or (Curr == NULL) )
   {
      Node * Temp;
      Temp = new Node;

      Temp->Item = A;
      Temp->Succ = Curr;
      Prev->Succ = Temp;
      Num++;
      Flag = true;
   }
   return Flag;
}

[Clockowl]

while ( (Curr->Item < A) and (Curr->Succ != NULL) )
   {
      Prev = Curr;
      Curr = Curr->Succ;
      cout << Curr->Item;
   }

That code sets Curr to the last item in the set that's smaller than A.
And then you compare the last item (curr->item) to A (to guarantee uniqueness) or NULL for the last item. And there's your problem I think, hehe.

What if Curr is NULL and you try to dereference Curr->item? Segfault. I hope that's the error.

So, correct code would be something like..

if(Curr == NULL){
//create new item, append it to the set
} else if (Curr->Item != A) {
//create new item, insert it between the two items.
}

[boydale1]

I don't really understand the last post. I do understand the second part, but I'm confused about the while loop still.

[Clockowl]

While the current node's item is smaller than A and the current item isn't NULL (and thus we are at the end of the list), go to the next node.