Beräkna tids- och minneskomplexiteten i värsta fallet (Ordo) för den länkade lista som finns i kursbokens tredje kapitel. Du kan hitta koden här.
Ange svaret i en tabell där varje metod har en egen rad med kolumner för tids- och minneskomplexiteten, enligt exemplet nedan. Motivera också dina svar och visa hur du kom fram till din lösning, även om lösningen verkar självklar.
| Metodnamn: | Tidskomplexitet: | Minneskomplexitet: |
| isEmpty() | O(N4) | O(0) |
| toString() | O(N42) | O(N) |
Observera att tabellen ovan bara är ett exempel. Du ska själv fylla i korrekta värden för Ordo för samtliga av listans metoder. Motiveringarna kan du antingen lägga in i tabellen eller skriva separat.
Inlämning
Du lämnar in din uppgift som en PDF-fil med dina svar. Tänk på att din inlämning ska vara anonym.
Totalt kan man få 100 poäng på veckans uppgift, varav 2x15 är för peer review. För att bli godkänd på uppgiften krävs att du får minst 90 poäng.
- Kod:
/**
* LinkedList class implements a doubly-linked list.
*/
public class MyLinkedList<AnyType> implements Iterable<AnyType>
{
/**
* Construct an empty LinkedList.
*/
public MyLinkedList( )
{
clear( );
}
/**
* Change the size of this collection to zero.
*/
public void clear( )
{
beginMarker = new Node<AnyType>( null, null, null );
endMarker = new Node<AnyType>( null, beginMarker, null );
beginMarker.next = endMarker;
theSize = 0;
}
/**
* Returns the number of items in this collection.
* @return the number of items in this collection.
*/
public int size( )
{
return theSize;
}
public boolean isEmpty( )
{
return size( ) == 0;
}
/**
* Adds an item to this collection, at the end.
* @param x any object.
* @return true.
*/
public boolean add( AnyType x )
{
add( size( ), x );
return true;
}
/**
* Adds an item to this collection, at specified position.
* Items at or after that position are slid one position higher.
* @param x any object.
* @param idx position to add at.
* @throws IndexOutOfBoundsException if idx is not between 0 and size(), inclusive.
*/
public void add( int idx, AnyType x )
{
addBefore( getNode( idx, 0, size( ) ), x );
}
/**
* Adds an item to this collection, at specified position p.
* Items at or after that position are slid one position higher.
* @param p Node to add before.
* @param x any object.
* @throws IndexOutOfBoundsException if idx is not between 0 and size(), inclusive.
*/
private void addBefore( Node<AnyType> p, AnyType x )
{
Node<AnyType> newNode = new Node<AnyType>( x, p.prev, p );
newNode.prev.next = newNode;
p.prev = newNode;
theSize++;
}
/**
* Returns the item at position idx.
* @param idx the index to search in.
* @throws IndexOutOfBoundsException if index is out of range.
*/
public AnyType get( int idx )
{
return getNode( idx ).data;
}
/**
* Changes the item at position idx.
* @param idx the index to change.
* @param newVal the new value.
* @return the old value.
* @throws IndexOutOfBoundsException if index is out of range.
*/
public AnyType set( int idx, AnyType newVal )
{
Node<AnyType> p = getNode( idx );
AnyType oldVal = p.data;
p.data = newVal;
return oldVal;
}
/**
* Gets the Node at position idx, which must range from 0 to size( ) - 1.
* @param idx index to search at.
* @return internal node corrsponding to idx.
* @throws IndexOutOfBoundsException if idx is not between 0 and size( ) - 1, inclusive.
*/
private Node<AnyType> getNode( int idx )
{
return getNode( idx, 0, size( ) - 1 );
}
/**
* Gets the Node at position idx, which must range from lower to upper.
* @param idx index to search at.
* @param lower lowest valid index.
* @param upper highest valid index.
* @return internal node corrsponding to idx.
* @throws IndexOutOfBoundsException if idx is not between lower and upper, inclusive.
*/
private Node<AnyType> getNode( int idx, int lower, int upper )
{
Node<AnyType> p;
if( idx < lower || idx > upper )
throw new IndexOutOfBoundsException( "getNode index: " + idx + "; size: " + size( ) );
if( idx < size( ) / 2 )
{
p = beginMarker.next;
for( int i = 0; i < idx; i++ )
p = p.next;
}
else
{
p = endMarker;
for( int i = size( ); i > idx; i-- )
p = p.prev;
}
return p;
}
/**
* Removes an item from this collection.
* @param idx the index of the object.
* @return the item was removed from the collection.
*/
public AnyType remove( int idx )
{
return remove( getNode( idx ) );
}
/**
* Removes the object contained in Node p.
* @param p the Node containing the object.
* @return the item was removed from the collection.
*/
private AnyType remove( Node<AnyType> p )
{
p.next.prev = p.prev;
p.prev.next = p.next;
theSize--;
return p.data;
}
/**
* Returns a String representation of this collection.
*/
public String toString( )
{
StringBuilder sb = new StringBuilder( "[ " );
for( AnyType x : this )
sb.append( x + " " );
sb.append( "]" );
return new String( sb );
}
/**
* Obtains an Iterator object used to traverse the collection.
* @return an iterator positioned prior to the first element.
*/
public java.util.Iterator<AnyType> iterator( )
{
return new LinkedListIterator( );
}
/**
* This is the implementation of the LinkedListIterator.
* It maintains a notion of a current position and of
* course the implicit reference to the MyLinkedList.
*/
private class LinkedListIterator implements java.util.Iterator<AnyType>
{
private Node<AnyType> current = beginMarker.next;
private boolean okToRemove = false;
public boolean hasNext( )
{
return current != endMarker;
}
public AnyType next( )
{
if( !hasNext( ) )
throw new java.util.NoSuchElementException( );
AnyType nextItem = current.data;
current = current.next;
okToRemove = true;
return nextItem;
}
public void remove( )
{
if( !okToRemove )
throw new IllegalStateException( );
MyLinkedList.this.remove( current.prev );
okToRemove = false;
}
}
/**
* This is the doubly-linked list node.
*/
private static class Node<AnyType>
{
public Node( AnyType d, Node<AnyType> p, Node<AnyType> n )
{
data = d; prev = p; next = n;
}
public AnyType data;
public Node<AnyType> prev;
public Node<AnyType> next;
}
private int theSize;
private Node<AnyType> beginMarker;
private Node<AnyType> endMarker;
}
class TestLinkedList
{
public static void main( String [ ] args )
{
MyLinkedList<Integer> lst = new MyLinkedList<Integer>( );
for( int i = 0; i < 10; i++ )
lst.add( i );
for( int i = 20; i < 30; i++ )
lst.add( 0, i );
lst.remove( 0 );
lst.remove( lst.size( ) - 1 );
System.out.println( lst );
java.util.Iterator<Integer> itr = lst.iterator( );
while( itr.hasNext( ) )
{
itr.next( );
itr.remove( );
System.out.println( lst );
}
}
}
Hem
vilka funktioner fick du?