1. COMPUTER 2430 Object Oriented Programming and Data Structures I

2. Sets A set is a collection of elements. Not sorted. No duplicates!
Can grow.
Examples
A = {1, 2, 3, 4}
B = {2, 5}
C = {1, 3, 5, 7, 9, 3}
Not a Set!

3. Set Class in Java public class Set { private final int INIT_SIZE = 5;
private final int GROWBY = 5;
private Object[] list = new Object[INIT_SIZE];
private int num = 0;
// Do we need the default constructor?
public Set() }
// Constructor with a given size
public Set(int size)
list = new Object[size];

4. Copy Constructor public class Set {
private Object[] list = new Object[INIT_SIZE];
private int num = 0;
public Set()
public Set(int size)
// Copy constructor
public Set(Set s)
this.list = new Object[s.length];
for (int i = 0; i < s.num; i ++)
this.list[i] = s.list[i];
this.num = s.num; }

5. public class Set {
private Object[] list = new Object[INIT_SIZE];
private int num = 0;
private int find( Object obj )
private void grow()
public boolean add( Object obj )
if (find(obj) != -1)
return false;
if (num == list.length)
grow();
list[num ++] = obj; // list[num] = obj; num ++;
return true; }

6. public class Set {
private Object[] list = new Object[INIT_SIZE];
private int num = 0;
private int find( Object obj )
private void grow()
public boolean remove( Object obj )
if (find(obj) == -1)
return false;
list[find(obj)] = list[num - 1];
num --;
return true; }

7. public class Set {
private Object[] list = new Object[INIT_SIZE];
private int num = 0;
private int find( Object obj )
private void grow()
public boolean remove( Object obj )
int index = find(obj);
if (index == -1)
return false;
list[index] = list[num - 1];
num --;
return true; }

8. public class Set {
private Object[] list = new Object[INIT_SIZE];
private int num = 0;
private int find( Object obj )
private void grow()
public boolean remove( Object obj )
int index = find(obj);
if (index == -1)
return false;
num --;
list[index] = list[num];
return true; }

9. public class Set {
private Object[] list = new Object[INIT_SIZE];
private int num = 0;
private int find( Object obj )
private void grow()
public boolean remove( Object obj )
int index = find(obj);
if (index == -1)
return false;
list[index] = list[-- num];
return true; }

10. public class Set {
private final int INIT_SIZE = 5;
private final int GROWBY = 5;
private Object[] list = new Object[INIT_SIZE];
private int num = 0;
// constructors
private int find( Object obj )
private void grow()
public boolean add( Object obj )
public boolean remove( Object obj )
public boolean isEmpty()
public int getCount()
public Object getItem( Object obj ) }

11. New Methods for Set Class
contains
intersection
union
difference
isSubsetOf
. . .

12. public class Set {
private Object[] list = new Object[INIT_SIZE];
private int num = 0;
/**
Usage examples: if (setA.contains(obj)) */
public boolean contains( Object obj )
return find(obj) != -1; }
private int find( Object obj )

13. Set Intersection A = {1, 2, 3, 4} B = {2, 5}
A  B = {x: x  A and x  B}
= {2}
= B  A

14. public class Set {
private Object[] list = new Object[INIT_SIZE];
private int num = 0;
/**
Usage example: setC = setA.intersection(setB)
Does not change either this or the parameter s! */
public Set intersection(Set s)
Set temp = new Set(num);
for (int i = 0; i < num; i ++)
if (s.conatins(list[i]))
temp.add(list[i])
return temp; }

15. public class Set {
private Object[] list = new Object[INIT_SIZE];
private int num = 0;
/**
Usage example: setC = setA.intersection(setB)
Does not change either this or the parameter s! */
public Set intersection(Set s)
Set temp = new Set(s.num);
for (int i = 0; i < s.num; i ++)
if (this.conatins(s.list[i]))
temp.add(s.list[i])
return temp; }

16. public class Set {
private Object[] list = new Object[INIT_SIZE];
private int num = 0;
/**
Usage example: setC = setA.intersection(setB)
Does not change either this or the parameter s! */
public Set intersection(Set s)
Set temp = new Set(); // will it work?
for (int i = 0; i < num; i ++)
if (s.conatins(list[i]))
temp.add(list[i])
return temp; }

17. Set Union A = {1, 2, 3, 4} B = {2, 5} A  B = {x: x  A or x  B}
= {1, 2, 3, 4, 5}
= B  A

18. Does it work? Other Better Way?
public class Set {
private Object[] list = new Object[INIT_SIZE];
private int num = 0;
/**
Usage example: setC = setA.union(setB)
Does not change either this or the parameter s! */
public Set union(Set s)
Set temp = new Set(this);
for (int i = 0; i < s.num; i ++)
if (!this.contains(s.list[i]))
temp.add(s.list[i])
return temp; }
Does it work?
Other Better Way?

19. Better and Do it this Way!
public class Set {
private Object[] list = new Object[INIT_SIZE];
private int num = 0;
/**
Usage example: setC = setA.union(setB)
Does not change either this or the parameter s! */
public Set union(Set s)
Set temp = new Set(this);
for (int i = 0; i < s.num; i ++)
temp.add(s.list[i])
return temp; }
Does it work?
Better and Do it this Way!

20. Set Difference A = {1, 2, 3, 4} B = {2, 5}
A – B = {x: x  A but x  B}
= {1, 3, 4}
 B- A
B – A = {5}

21. public class Set {
private Object[] list = new Object[INIT_SIZE];
private int num = 0;
/**
Usage example: setC = setA.difference(setB)
Does not change either this or the parameter s! */
public Set difference(Set s)
Set temp = new Set(this);
for (int i = 0; i < s.num; i ++)
temp.remove(s.list[i])
return temp; }

22. Subset For two sets A and B and any element x, if x  A then x  B
Then A is a subset of B
A  B or B  A
A = {1, 2, 3, 4} B = {2, 5} C = {1, 3}
B  A?
C  A?

23. public class Set {
private Object[] list = new Object[INIT_SIZE];
private int num = 0;
/**
Usage example: if (setA.isSubsetOf(setB))
Does not change either this or the parameter s! */
public boolean isSubsetOf(Set s)
for (int i = 0; i < num; i ++)
if (! s.contains(list[i])
return false;
return true; }

24. Prog 2
Friday: Class in Lab 206