Set Data Type (9.1)

















What's a Set?


	1. a container that holds objects
	2. no duplicates
	3. the container controls the order of the objects

















What operations are supported by a Set?
What's the abstract interface for a Set?


	size();
	add(item);
	remove(item);
	find(item);



What happens if you add 2 to a set that already contains 2?

What order is commonly used for the items in a Set?

















Classwork
You may work with a partner.

What does the program print?

	Set S1;
	S1.add(4);
	S1.add(2);
	S1.add(8);
	S1.add(4);
	S1.add(1);
	S1.add(8);
	print(S1);

	Set S2;
	for ( item : S1 )
	    S2.add( item );
	print(S2);

	S1.remove(2);
	S1.remove(4);
	print(S1);

	for ( item : S1 )
	    S2.remove( item );
	print(S2);

















Sets in the C++ Library


	#include <set>

	std::set

















What are some of the operations supported by std::set?


	size_t size() const;
	pair<iterator,bool> insert ( const ItemType& item );
	size_t erase ( const ItemType& item ); // returns number of items erased
	iterator find ( const ItemType& item ) const;
	size_t count ( const ItemType& item ) const;


DEMO	(change list to set)

















Why Set?


A List holds a collection of objects and
allows you to control each object's location.

A Set holds a collection of objects but
does not allow you to control object location.

Why is a Set useful?


DEMO	(time for find on list vs set)