Java - bag adt with linked list

  • Comp Sci
  • Thread starter schapman22
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In summary: If the new elements would take this bag beyond its current capacity, then * the capacity is increased before adding the new elements. * @param addend * (a new bag whose contents will be added to this bag) * @return this bag after adding the elements. **/ public IntLinkedBag add(IntLinkedBag[] elements, int capacity, IntLinkedBag addend) { // If addend is not null, then it must be
  • #1
schapman22
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0

Homework Statement


"Implement a new method for the bag class. The new method allows you to subtract the contents of one bag from another. For example, suppose x has seven copies of the number 3 and y has two copies of the number 3. Then after activating x.subtract(y), the bag x will have five remaining copies of the number 3. "


Homework Equations


This is the bag class, it is implemented with a linked list. It uses another class called IntNode, the methods from this class can be used as well so i add both classes.

Code:
// File: IntLinkedBag.java from the package edu.colorado.linked
// Complete documentation is available from the IntLinkedBag link in:
//   http://www.cs.colorado.edu/~main/docs

package edu.colorado.collections;
import edu.colorado.nodes.IntNode; 

/******************************************************************************
* An IntLinkedBag is a collection of int numbers.
*
* @note
*   (1) Beyond Int.MAX_VALUE elements, countOccurrences,
*   size, and grab are wrong.
*   <p>
*   (2) Because of the slow linear algorithms of this class, large bags will have
*   poor performance.
*
* @see
*   <A HREF="../../../../edu/colorado/collections/IntLinkedBag.java">
*   Java Source Code for this class
*   (www.cs.colorado.edu/~main/edu/colorado/collections/IntLinkedBag.java)
*   </A>
*
* @author Michael Main 
*   <A HREF="mailto:main@colorado.edu"> (main@colorado.edu) </A>
*
* @version
*   March 6, 2002
*
* @see IntArrayBag
* @see LinkedBag
******************************************************************************/
public class IntLinkedBag implements Cloneable
{
   // Invariant of the IntLinkedBag class:
   //   1. The elements in the bag are stored on a linked list.
   //   2. The head reference of the list is in the instance variable 
   //      head.
   //   3. The total number of elements in the list is in the instance 
   //      variable manyNodes.
   private IntNode head;
   private int manyNodes;   


   /**
   * Initialize an empty bag.
   * @param - none
   * @postcondition
   *   This bag is empty.
   **/
   public IntLinkedBag( )
   {
      head = null;
      manyNodes = 0;
   }
        
 
   /**
   * Add a new element to this bag.
   * @param element
   *   the new element that is being added
   * @postcondition
   *   A new copy of the element has been added to this bag.
   * @exception OutOfMemoryError
   *   Indicates insufficient memory a new IntNode.
   **/
   public void add(int element)
   {      
      head = new IntNode(element, head);
      manyNodes++;
   }


   /**
   * Add the contents of another bag to this bag.
   * @param addend
   *   a bag whose contents will be added to this bag
   * @precondition
   *   The parameter, addend, is not null.
   * @postcondition
   *   The elements from addend have been added to this bag.
   * @exception NullPointerException
   *   Indicates that addend is null.
   * @exception OutOfMemoryError
   *   Indicates insufficient memory to increase the size of the bag.
   **/
   public void addAll(IntLinkedBag addend)
   {
      IntNode[ ] copyInfo;
      
      // The precondition indicates that addend is not null. If it is null,
      // then a NullPointerException is thrown here.
      if (addend.manyNodes > 0)
      {
         copyInfo = IntNode.listCopyWithTail(addend.head);
         copyInfo[1].setLink(head); // Link the tail of copy to my own head... 
         head = copyInfo[0];        // and set my own head to the head of the copy.
         manyNodes += addend.manyNodes;
      }
   }

     
   /**
   * Add new elements to this bag. If the new elements would take this
   * bag beyond its current capacity, then the capacity is increased
   * before adding the new elements.
   * @param elements
   *   (a variable-arity argument)
   *   one or more new elements that are being inserted
   * @postcondition
   *   A new copy of the element has been added to this bag.
   * @exception OutOfMemoryError
   *   Indicates insufficient memory to increase the size of the bag.
   **/
   public void addMany(int... elements)
   {
      // Activate the ordinary add method for each integer in the
      // elements array.
      for (int i : elements)
          add(i); 	       
   }

     
   /**
   * Generate a copy of this bag.
   * @param - none
   * @return
   *   The return value is a copy of this bag. Subsequent changes to the
   *   copy will not affect the original, nor vice versa. Note that the return
   *   value must be type cast to an IntLinkedBag before it can be used.
   * @exception OutOfMemoryError
   *   Indicates insufficient memory for creating the clone.
   **/ 
   public Object clone( )
   {  // Clone a nIntLinkedBag object.
      IntLinkedBag answer;
      
      try
      {
         answer = (IntLinkedBag) super.clone( );
      }
      catch (CloneNotSupportedException e)
      {  // This exception should not occur. But if it does, it would probably
         // indicate a programming error that made super.clone unavailable.
         // The most common error would be forgetting the "Implements Cloneable"
         // clause at the start of this class.
         throw new RuntimeException
         ("This class does not implement Cloneable");
      }
      
      answer.head = IntNode.listCopy(head);
      
      return answer;
   }
   

   /**
   * Accessor method to count the number of occurrences of a particular element
   * in this bag.
   * @param target
   *   the element that needs to be counted
   * @return
   *   the number of times that target occurs in this bag
   **/
   public int countOccurrences(int target)
   {
      int answer;
      IntNode cursor;

      answer = 0;
      cursor = IntNode.listSearch(head, target);
      while (cursor != null)
      {  // Each time that cursor is not null, we have another occurrence of
         // target, so we add one to answer and then move cursor to the next
         // occurrence of the target.
         answer++;
         cursor = cursor.getLink( );
         cursor = IntNode.listSearch(cursor, target);
      }
      return answer;
   }

    
   /**
   * Accessor method to retrieve a random element from this bag.
   * @param - none
   * @precondition
   *   This bag is not empty.
   * @return
   *   a randomly selected element from this bag
   * @exception IllegalStateException
   *   Indicates that the bag is empty.
   **/
   public int grab( )
   {
      int i;
      IntNode cursor;
      
      if (manyNodes == 0)
         throw new IllegalStateException("Bag size is zero");
         
      i =  (int)(Math.random( ) * manyNodes) + 1;
      cursor = IntNode.listPosition(head, i);
      return cursor.getData( );
   }
   
             
   /**
   * Remove one copy of a specified element from this bag.
   * @param target
   *   the element to remove from the bag
   * @postcondition
   *   If target was found in the bag, then one copy of
   *   target has been removed and the method returns true. 
   *   Otherwise the bag remains unchanged and the method returns false. 
   **/
   public boolean remove(int target)
   {
      IntNode targetNode; // The node that contains the target

      targetNode = IntNode.listSearch(head, target);
      if (targetNode == null)
         // The target was not found, so nothing is removed.
         return false;
      else
      {  // The target was found at targetNode. So copy the head data to targetNode
         // and then remove the extra copy of the head data.
         targetNode.setData(head.getData( ));
         head = head.getLink( );
         manyNodes--;
         return true;
      }
   }
    
      
   /**
   * Determine the number of elements in this bag.
   * @param - none
   * @return
   *   the number of elements in this bag
   **/                           
   public int size( )
   {
      return manyNodes;
   }
   

   /**
   * Create a new bag that contains all the elements from two other bags.
   * @param b1
   *   the first of two bags
   * @param b2
   *   the second of two bags
   * @precondition
   *   Neither b1 nor b2 is null.
   * @return
   *   the union of b1 and b2
   * @exception IllegalArgumentException
   *   Indicates that one of the arguments is null.
   * @exception OutOfMemoryError
   *   Indicates insufficient memory for the new bag.
   **/   
   public static IntLinkedBag union(IntLinkedBag b1, IntLinkedBag b2)
   {       
      // The precondition requires that neither b1 nor b2 is null.
      // If one of them is null, then addAll will throw a NullPointerException.  
      IntLinkedBag answer = new IntLinkedBag( );
      
      answer.addAll(b1);
      answer.addAll(b2);     
      return answer;
   }
   
   public void getBagData()
   {
       IntNode b1 = this.head;
       for(IntNode cursor=b1; cursor!=null; cursor=cursor.getLink())
           System.out.println(cursor.getData());
   }
      
}

The Attempt at a Solution


this is my incomplete attempt.

Code:
public IntLinkedBag subtract(IntLinkedBag b2)
   {
       IntNode bag1 = this.head;
       IntNode bag2 = b2.head;
       
       for(IntNode cursor=bag1; cursor!=null; cursor=cursor.getLink())
           //remove if same as bag2
       return this;
   }
 
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  • #2
This is the IntNode class that is used.

Code:
// File: IntNode.java from the package edu.colorado.nodes
// Complete documentation is available from the IntNode link in:
//   http://www.cs.colorado.edu/~main/docs

package edu.colorado.nodes;

/******************************************************************************
* An IntNode provides a node for a linked list with 
* integer data in each node.
*
* @note
*   Lists of nodes can be made of any length, limited only by the amount of
*   free memory in the heap. But beyond Integer.MAX_VALUE (2,147,483,647),
*   the answer from listLength is incorrect because of arithmetic
*   overflow. 
*
* @see
*   <A HREF="../../../../edu/colorado/nodes/IntNode.java">
*   Java Source Code for this class
*   (www.cs.colorado.edu/~main/edu/colorado/nodes/IntNode.java)</A>
*
* @author Michael Main 
*   <A HREF="mailto:main@colorado.edu"> (main@colorado.edu) </A>
*
* @version
*   March 6, 2002
*
* @see Node
* @see BooleanNode
* @see ByteNode
* @see CharNode
* @see DoubleNode
* @see FloatNode
* @see LongNode
* @see ShortNode
******************************************************************************/
public class IntNode
{
   // Invariant of the IntNode class:
   //   1. The node's integer data is in the instance variable data.
   //   2. For the final node of a list, the link part is null.
   //      Otherwise, the link part is a reference to the
   //      next node of the list.
   private int data;
   private IntNode link;   


   /**
   * Initialize a node with a specified initial data and link to the next
   * node. Note that the initialLink may be the null reference, 
   * which indicates that the new node has nothing after it.
   * @param initialData
   *   the initial data of this new node
   * @param initialLink
   *   a reference to the node after this new node--this reference may be null
   *   to indicate that there is no node after this new node.
   * @postcondition
   *   This node contains the specified data and link to the next node.
   **/   
   public IntNode(int initialData, IntNode initialLink)
   {
      data = initialData;
      link = initialLink;
   }


   /**
   * Modification method to add a new node after this node.   
   * @param item
   *   the data to place in the new node
   * @postcondition
   *   A new node has been created and placed after this node.
   *   The data for the new node is item. Any other nodes
   *   that used to be after this node are now after the new node.
   * @exception OutOfMemoryError
   *   Indicates that there is insufficient memory for a new 
   *   IntNode. 
   **/
   public void addNodeAfter(int item)   
   {
      link = new IntNode(item, link);
   }          
   
   
   /**
   * Accessor method to get the data from this node.   
   * @param - none
   * @return
   *   the data from this node
   **/
   public int getData( )   
   {
      return data;
   }
   
   
   /**
   * Accessor method to get a reference to the next node after this node. 
   * @param - none
   * @return
   *   a reference to the node after this node (or the null reference if there
   *   is nothing after this node)
   **/
   public IntNode getLink( )
   {
      return link;                                               
   } 
    
    
   /**
   * Copy a list.
   * @param source
   *   the head of a linked list that will be copied (which may be
   *   an empty list in where source is null)
   * @return
   *   The method has made a copy of the linked list starting at 
   *   source. The return value is the head reference for the
   *   copy. 
   * @exception OutOfMemoryError
   *   Indicates that there is insufficient memory for the new list.   
   **/ 
   public static IntNode listCopy(IntNode source)
   {
      IntNode copyHead;
      IntNode copyTail;
      
      // Handle the special case of the empty list.
      if (source == null)
         return null;
         
      // Make the first node for the newly created list.
      copyHead = new IntNode(source.data, null);
      copyTail = copyHead;
      
      // Make the rest of the nodes for the newly created list.
      while (source.link != null)
      {
         source = source.link;
         copyTail.addNodeAfter(source.data);
         copyTail = copyTail.link;
      }
 
      // Return the head reference for the new list.
      return copyHead;
   }
   
   
   /**
   * Copy a list, returning both a head and tail reference for the copy.
   * @param source
   *   the head of a linked list that will be copied (which may be
   *   an empty list in where source is null)
   * @return
   *   The method has made a copy of the linked list starting at 
   *   source.  The return value is an
   *   array where the [0] element is a head reference for the copy and the [1]
   *   element is a tail reference for the copy.
   * @exception OutOfMemoryError
   *   Indicates that there is insufficient memory for the new list.   
   **/
   public static IntNode[ ] listCopyWithTail(IntNode source)
   {
      IntNode copyHead;
      IntNode copyTail;
      IntNode[ ] answer = new IntNode[2];
     
      // Handle the special case of the empty list.   
      if (source == null)
         return answer; // The answer has two null references .
      
      // Make the first node for the newly created list.
      copyHead = new IntNode(source.data, null);
      copyTail = copyHead;
      
      // Make the rest of the nodes for the newly created list.
      while (source.link != null)
      {
         source = source.link;
         copyTail.addNodeAfter(source.data);
         copyTail = copyTail.link;
      }
      
      // Return the head and tail references.
      answer[0] = copyHead;
      answer[1] = copyTail;
      return answer;
   }
   
   
   /**
   * Compute the number of nodes in a linked list.
   * @param head
   *   the head reference for a linked list (which may be an empty list
   *   with a null head)
   * @return
   *   the number of nodes in the list with the given head 
   * @note
   *   A wrong answer occurs for lists longer than Int.MAX_VALUE.     
   **/   
   public static int listLength(IntNode head)
   {
      IntNode cursor;
      int answer;
      
      answer = 0;
      for (cursor = head; cursor != null; cursor = cursor.link)
         answer++;
        
      return answer;
   }
   

   /**
   * Copy part of a list, providing a head and tail reference for the new copy. 
   * @param start/end
   *   references to two nodes of a linked list
   * @param copyHead/copyTail
   *   the method sets these to refer to the head and tail node of the new
   *   list that is created
   * @precondition
   *   start and end are non-null references to nodes
   *   on the same linked list,
   *   with the start node at or before the end node. 
   * @return
   *   The method has made a copy of the part of a linked list, from the
   *   specified start node to the specified end node. The return value is an
   *   array where the [0] component is a head reference for the copy and the
   *   [1] component is a tail reference for the copy.
   * @exception IllegalArgumentException
   *   Indicates that start and end are not references
   *   to nodes on the same list.
   * @exception NullPointerException
   *   Indicates that start is null.
   * @exception OutOfMemoryError
   *   Indicates that there is insufficient memory for the new list.    
   **/   
   public static IntNode[ ] listPart(IntNode start, IntNode end)
   {
      IntNode copyHead;
      IntNode copyTail;
      IntNode cursor;
      IntNode[ ] answer = new IntNode[2];
      
      // Make the first node for the newly created list. Notice that this will
      // cause a NullPointerException if start is null.
      copyHead = new IntNode(start.data, null);
      copyTail = copyHead;
      cursor = start;
      
      // Make the rest of the nodes for the newly created list.
      while (cursor != end)
      {
         cursor = cursor.link;
         if (cursor == null)
            throw new IllegalArgumentException
            ("end node was not found on the list");
         copyTail.addNodeAfter(cursor.data);
         copyTail = copyTail.link;
      }
      
      // Return the head and tail references
      answer[0] = copyHead;
      answer[1] = copyTail;
      return answer;
   }        
   
   
   /**
   * Find a node at a specified position in a linked list.
   * @param head
   *   the head reference for a linked list (which may be an empty list in
   *   which case the head is null)
   * @param position
   *   a node number
   * @precondition
   *   position > 0.
   * @return
   *   The return value is a reference to the node at the specified position in
   *   the list. (The head node is position 1, the next node is position 2, and
   *   so on.) If there is no such position (because the list is too short),
   *   then the null reference is returned.
   * @exception IllegalArgumentException
   *   Indicates that position is not positive.    
   **/   
   public static IntNode listPosition(IntNode head, int position)
   {
      IntNode cursor;
      int i;
      
      if (position <= 0)
           throw new IllegalArgumentException("position is not positive");
      
      cursor = head;
      for (i = 1; (i < position) && (cursor != null); i++)
         cursor = cursor.link;

      return cursor;
   }


   /**
   * Search for a particular piece of data in a linked list.
   * @param head
   *   the head reference for a linked list (which may be an empty list in
   *   which case the head is null)
   * @param target
   *   a piece of data to search for
   * @return
   *   The return value is a reference to the first node that contains the
   *   specified target. If there is no such node, the null reference is 
   *   returned.     
   **/   
   public static IntNode listSearch(IntNode head, int target)
   {
      IntNode cursor;
      
      for (cursor = head; cursor != null; cursor = cursor.link)
         if (target == cursor.data)
            return cursor;
        
      return null;
   }

   
   /**
   * Modification method to remove the node after this node.   
   * @param - none
   * @precondition
   *   This node must not be the tail node of the list.
   * @postcondition
   *   The node after this node has been removed from the linked list.
   *   If there were further nodes after that one, they are still
   *   present on the list.
   * @exception NullPointerException
   *   Indicates that this was the tail node of the list, so there is nothing
   *   after it to remove.
   **/
   public void removeNodeAfter( )   
   {
      link = link.link;
   }          
   
   
   /**
   * Modification method to set the data in this node.   
   * @param newData
   *   the new data to place in this node
   * @postcondition
   *   The data of this node has been set to newData.
   **/
   public void setData(int newData)   
   {
      data = newData;
   }                                                               
   
   
   /**
   * Modification method to set the link to the next node after this node.
   * @param newLink
   *   a reference to the node that should appear after this node in the linked
   *   list (or the null reference if there is no node after this node)
   * @postcondition
   *   The link to the node after this node has been set to newLink.
   *   Any other node (that used to be in this link) is no longer connected to
   *   this node.
   **/
   public void setLink(IntNode newLink)
   {                    
      link = newLink;
   }
   
   public void printRange(IntNode head, int x, int y)
   {
       for (IntNode cursor = head; cursor!=null; cursor = cursor.link)
       {
           if(cursor.data>=x && cursor.data<=y)
               System.out.println(cursor.data);
       }
   }
   
   public static IntNode removeDuplicates(IntNode h)
   {
       IntNode copyHead = new IntNode (h.data, null);
       IntNode cursor2 = copyHead;

       for(IntNode cursor=h.link;cursor!=null; cursor=cursor.link)
       {
           if(!(IntNode.listSearch2(copyHead,cursor.data)))
           {
              cursor2.addNodeAfter(cursor.data);
              cursor2 = cursor2.link;
           }
        }
       return copyHead;
   }

   public static boolean listSearch2(IntNode head, int target)
   {
      IntNode cursor;

      for (cursor = head; cursor != null; cursor = cursor.link)
         if (target == cursor.data)
            return true;

      return false;
   }
   
    public static IntNode reverseList(IntNode head) 
    {

        int i;
        int length = IntNode.listLength(head);
        IntNode copyHead, cursor;
        IntNode copyTail = IntNode.listPosition(head, length);
        copyHead = new IntNode(copyTail.data, null);
        cursor = copyHead;
        for (i = length - 1; i >= 1; i--) 
        {
            copyTail = IntNode.listPosition(head, i);
            cursor.addNodeAfter(copyTail.data);
            cursor = cursor.getLink();
        }
        return copyHead;
    }
   
   public static IntNode listSort(IntNode head)
   {
        IntNode cursor;
        int largest;
        IntNode copyHead=null;
        IntNode target;
        while(head!=null)
        {
            target = head;
            largest = head.data;
            for(cursor=head.link;cursor!=null;cursor=cursor.link)
            {
                if(cursor.data > largest)
                {
                    target=cursor;
                    largest=cursor.data;
                }
            }
            copyHead = new IntNode(target.data, copyHead);
            target.setData(head.data);
            head=head.link;
        }
        return copyHead;
    }
       
}
 
  • #3
I think I got it working properly, let me know if you find any bugs.

Code:
public IntLinkedBag subtract(IntLinkedBag b2)
   {
       IntNode bag1 = this.head;
       IntNode bag2 = b2.head;
       IntNode cursor;
 
            for(cursor=bag2; cursor!=null; cursor=cursor.getLink())
            {
                if(bag1.getData()==cursor.getData())
                    this.remove(bag1.getData());
                bag1=bag1.getLink();
            }
       return this;
   }
 

1. What is an ADT in Java?

An ADT (Abstract Data Type) in Java is a data structure that encapsulates data and operations on that data. It is an abstraction that defines the behavior of a data type without specifying its implementation. This allows for flexibility and modularity in programming.

2. How is a bag ADT implemented using a linked list in Java?

A bag ADT implemented with a linked list in Java stores data in a linear data structure where each element points to the next element. The first element is called the head and the last element points to null. This allows for efficient insertion and deletion of elements at the beginning or end of the list.

3. What are the advantages of using a linked list to implement a bag ADT in Java?

There are several advantages to using a linked list to implement a bag ADT in Java. Firstly, it allows for dynamic memory allocation, meaning the size of the list can change at runtime. Secondly, insertion and deletion operations are efficient as they only require adjusting the pointers, rather than shifting elements in an array. Lastly, linked lists can be easily traversed in both directions, unlike arrays which can only be traversed in one direction.

4. How do you add an element to a bag ADT implemented with a linked list in Java?

To add an element to a bag ADT implemented with a linked list in Java, you first create a new node with the data to be added. Then, set the next pointer of the new node to point to the head of the list. Finally, set the head pointer to point to the new node, effectively adding the element to the beginning of the list.

5. Can elements in a bag ADT implemented with a linked list in Java be accessed randomly?

No, elements in a bag ADT implemented with a linked list in Java cannot be accessed randomly. Linked lists do not have indices like arrays, and each element can only be accessed by traversing the list starting from the head or tail. To access a specific element, you would need to traverse through the list until you reach the desired element.

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