Matrix and Linked List ADTs

1
Matrix and Linked List ADTs

• B.Ramamurthy
• (Still in Chapter 4)

2
Topics for Discussion

• Matrix interface
• And an implementation
• Singly-linked List
• Linked List from Java API
• Summary

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Matrix Interface

• public interface Matrix
• double get (int i, int j)
• void put (int i, int j, double d)
• Matrix transpose()
• Matrix times (Matrix matrix)
• Matrix plus (Matrix matrix)

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An Implementation Dense Matrix

• From an interface definition there can be many
  implementations.
• For example, dense matrix, sparse matrix,
  triangular matrix, may have different semantics
  for the methods specified in the interface.

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Data Fields and Constructor

• public class DenseMatrix implements Matrix
• protected int numberOfRows
• protected int numberOfColumns
• protected double array
• public DenseMatrix (int numberOfRows, int
  numberOfColumns)
• this.numberOfRows numberOfRows
• this.numberOfColumns numberOfColumns
• array new doublenumberOfRowsnumberOfColumn
  s
• //others

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times method

• public Matrix times (Matrix mat)
• DenseMatrix arg (DenseMatrix) mat
• if (numberOfColumns ! arg.numberOfRows)
• // throw exception
• DenseMatrix result new DenseMatrix(numberOfRow
  s, arg.numberOfColumns)

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times method (contd.)

• for (int j 0 jlt numberOfRows j)
• for (int k 0 klt arg.numberOfColumnsk)
• double sum 0
• for (int p 0 plt numberOfColumns p)
• sum sum arrayjp argpk
• result.arrayjk sum
• return result

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Linked List

• Linked data representation and algorithms that
  manipulate them are an important component of
  study in CS.
• Linked representations are used when it is
  difficult to predict the size and shape of the
  data structures needed.

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A node of linked list
public class ListNode ItemType item ListNode
link some times you have explicit
representation for a head and or tail.
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Linked List class
LinkedList
// data int length ListNode firstNode //
methods public int size() public bool
insertNode(ItemType it) public bool
insertLast(ItemType it) public bool
deleteLast() public ListNode search(ItemType
it) public bool equals(LinkedList ll) public
String toString()
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JDK1.2 Linked List
Object
AbstractCollection
Collection
AbstractList
List
AbstractSequentialList
List, java.io.Serializable, java.lang.Cloneable
LinkedList
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LinkedLists inheritance

• Most of the direct linked list functionality is
  defined in the interface List.
• Serializable defines the disk archiving
  functionality.
• Cloenable defined the cloning ability.
• LinkedList class defines the variables needed for
  storing the header and size.
• A ListIterator class offers the Iterator facility.

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LinkedList methods

• List interface and how LinkedList implements
  them.
• Look at /util/lang/jdk1.2/docs/index.html for
  more details.
• Among the methods a special method called
  iterator is important many of the Collection
  classes. This is proper way carry out an
  operation on on all elements of a collection.

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ListIterator

• Usage
• LinkedList myList new LinkedList()
• // fill it up with data
• ListIterator k myList.listIterator()
• while(k.hasNext())
• // process the elements
• myProcess(k.next())
• System.out.println(k.next())