COMPUTER 2430 Object Oriented Programming and Data Structures I

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!

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];

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; }

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; }

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; }

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; }

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; }

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; }

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 ) }

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

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 )

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

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; }

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; }

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; }

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

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?

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!

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}

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; }

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?

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; }

Prog 2 Friday: Class in Lab 206