1. Abstract Data Types
ADT: A set of objects and a set of operations on those objects.
examples:
integers: +, - , *, …
Collection, insert, remove, …
set: union, intersection, complement, size, …
In C++, the set of operations roughly corresponds to the public member functions of a class.
Oct 12, 2001
CSE 373, Autumn 2001

2. ADTs continued
Implementation details can be hidden: member functions access private data members and member functions.
Functions outside the ADT can only access the public data members and functions.
difference between software engineering and hacking: finding the balance between functionality, simplicity, flexibility, and performance.
ADT
Oct 12, 2001
CSE 373, Autumn 2001

3. List ADT list of size N: A1, A2, A3, …, AN The position of Ai is i.
A list of size 0 is the empty list.
operations :
printList ( )
makeEmpty ( )
insert (x, pos)
remove (x)
findkth (k) …
Oct 12, 2001
CSE 373, Autumn 2001

4. Array Implementation printList makeEmpty insert remove findkth
Problems? A1 A2 A3 … AN
Oct 12, 2001
CSE 373, Autumn 2001

5. Linked List Impl. insert delete A1 A2 A3 A4 x A1 A2 A3 A4 Oct 12, 2001
CSE 373, Autumn 2001

6. Sentinels Use a header or dummy node to simplify the code. header
empty list A1 A2 A3
Oct 12, 2001
CSE 373, Autumn 2001

7. Linked Lists in C++
Weiss uses three classes to implement linked lists.
IntListItr
IntList A1 A2 A3
IntListNode
Oct 12, 2001
CSE 373, Autumn 2001

8. IntListNode IntListNode represents one node of a list.
class IntListNode {
private:
IntListNode (const int theData = 0,
IntListNode * n = NULL)
: data(theData), next(n) }
int data;
IntListNode * next;
friend class IntList;
friend class IntListItr; };
IntListNode represents one node of a list.
Oct 12, 2001
CSE 373, Autumn 2001

9. IntListItr class IntListItr { public: IntListItr() : current(NULL) { }
bool isPastEnd() const
return (current == NULL); }
void advance()
if (!isPastEnd())
current = current->next;
const int retrieve() const
if (isPastEnd())
throw BadIterator();
return current->data;
Oct 12, 2001
CSE 373, Autumn 2001

10. IntListNode * current; IntListItr(IntListNode * theNode)
private:
IntListNode * current;
IntListItr(IntListNode * theNode)
: current(theNode) { }
friend class IntList;
} // class IntListItr
class IntList {
public:
// constructors ...
bool isEmpty() const;
void makeEmpty();
IntListItr zeroth() const;
...
void insert (const int x,
const IntListItr & p);
IntListNode *header; }
Oct 12, 2001
CSE 373, Autumn 2001

11. IntList functions IntList::IntList() { header = new IntListNode; }
bool IntList::isEmpty() const
return (header->next == NULL);
IntListItr IntList::first() const
return IntListItr(header->next);
IntListItr IntList::find(const int x) const
IntListNode *itr = header->next;
while ((itr != NULL) && (itr->data != x))
itr = itr->next;
return IntListItr(itr);
Oct 12, 2001
CSE 373, Autumn 2001