CODEWITHSUNDEEP
java
Chc
Chc

Reputation: 47

Java count function not working. Console application array of numbers

I am having trouble with my int count(int i) function: The function should count the number of occurrences a number appears in the List. For example there is an array of numbers 3 4 4 1 3 2 1 This is what it should display:

Item 0  count = 0
Item 1  count = 2
Item 2  count = 1
Item 3  count = 2
Item 4  count = 2
Item 5  count = 0

class Bag
{
private Node first;  //dummy header node

// Initializes the list to empty creating a dummy header node.
public Bag()
{
    first = new Node();
}

// Returns true if the list is empty, false otherwise
public boolean isEmpty()
{
    return (first.getNext() == null);
}

// Clears all elements from the list
public void clear()
{
    first.setNext(null);
}

// Returns the number of item in the list
public int getLength()
{
    int length = 0;
    Node current = first.getNext();
    while (current != null)
    {
        length++;
        current = current.getNext();
    }
    return length;
}

// Prints the list elements.
public String toString()
{
    String list = "";
    Node current = first.getNext();
    while (current != null)
    {
        list += current.getInfo() + " ";
        current = current.getNext();
    }
    return list;
}

// Adds the element x to the beginning of the list.
public void add(int x)
{
    Node p = new Node();
    p.setInfo(x);
    p.setNext(first.getNext());
    first.setNext(p);
}

// Deletes an item x from the list. Only the first
// occurrence of the item in the list will be removed.
public void remove(int x)
{
    Node old = first.getNext();
    Node p = first;

    //Finding the reference to the node before the one to be deleted
    boolean found = false;
    while (old != null && !found)
    {
        if (old.getInfo() == x)
            found = true;
        else
        {
            p = old;
            old = p.getNext();
        }
    }

    //if x is in the list, remove it.
    if (found)
        p.setNext(old.getNext());
}

//public int count(int item) {
  // int count = 0;

   //for(int i = 0; i < length; i++) {
    //   if(bag[i] == item) {
    //     count++;
      // }
   //}

  // return count;
//}


// Inner class Node.
private class Node
{
    private int info;   //element stored in this node
    private Node next;  //link to next node

    // Initializes this node setting info to 0 and next to null
    public Node()
    {
        info = 0;
        next = null;
    }

    // Sets the value for this node
    public void setInfo(int i)
    {
        info = i;
    }

    // Sets the link to the next node
    public void setNext(Node lnk)
    {
        next = lnk;
    }

    // Returns the value in this node
    public int getInfo()
    {
        return info;
    }

    // Returns the link to the next node
    public Node getNext()
    {
        return next;
    }
}
}

// Class implementing a linked list.
class LinkedList
{
private Node first;  //dummy header node

// Initializes the list to empty creating a dummy header node.
public LinkedList()
{
    first = new Node();
}

// Returns true if the list is empty, false otherwise
public boolean isEmpty()
{
    return (first.getNext() == null);
}

// Clears all elements from the list
public void clear()
{
    first.setNext(null);
}

// Returns the number of item in the list
public int getLength()
{
    int length = 0;
    Node current = first.getNext();
    while (current != null)
    {
        length++;
        current = current.getNext();
    }
    return length;
}

// Prints the list elements.
public String toString()
{
    String list = "";
    Node current = first.getNext();
    while (current != null)
    {
        list += current.getInfo() + " ";
        current = current.getNext();
    }
    return list;
}

// Adds the element x to the beginning of the list.
public void add(int x)
{
    Node p = new Node();
    p.setInfo(x);
    p.setNext(first.getNext());
    first.setNext(p);
}

// Deletes an item x from the list. Only the first
// occurrence of the item in the list will be removed.
public void remove(int x)
{
    Node old = first.getNext();
    Node p = first;

    //Finding the reference to the node before the one to be deleted
    boolean found = false;
    while (old != null && !found)
    {
        if (old.getInfo() == x)
            found = true;
        else
        {
            p = old;
            old = p.getNext();
        }
    }

    //if x is in the list, remove it.
    if (found)
        p.setNext(old.getNext());
}

// Returns the element at a given location in the list
public int get(int location)
{
    int item = -1;
    int length = getLength();

    if (location <1 || location > length)
        System.out.println("\nError: Attempted get location out of range.");
    else
    {
        int n = 1;
        Node current = first.getNext();
        while (n < location)
        {
            n++;
            current = current.getNext();
        }
        item = current.getInfo();
    }
    return item;
}

/************************************************************************
 Students to complete the following two methods for the LinkedList class
 ***********************************************************************/
// Adds item to the end of the list
public void addEnd(int item)
{
    Node currentPos = new Node();
    Node newPos = new Node(); //create a new node
    newPos.setInfo(item); //load the data
    currentPos = first;

        while(currentPos.getNext() !=null)
        {
            currentPos = currentPos.getNext();
        }
        currentPos.setNext(newPos);
}

// Replaces the info in the list at location with item
public void replace(int location, int item)
{
    Node currentPos = new Node();
    Node prevPos = new Node();
    Node nextPos = new Node();
    int length = getLength();

    if (location <1 || location > length)
        System.out.println("\nError: Attempted get location out of range.");
    else
    {
        prevPos = first;
        for(int i=0; i < location-1; i++)
        {
            prevPos = prevPos.getNext();
        }
        currentPos = prevPos.getNext();
        nextPos = currentPos.getNext();
        Node newPos = new Node();
        newPos.setInfo(item);
        newPos.setNext(nextPos);
        prevPos.setNext(newPos);    
    }
}

// Inner class Node.
private class Node
{
    private int info;   //element stored in this node
    private Node next;  //link to next node

    // Initializes this node setting info to 0 and next to null
    public Node()
    {
        info = 0;
        next = null;
    }

    // Sets the value for this node
    public void setInfo(int i)
    {
        info = i;
    }

    // Sets the link to the next node
    public void setNext(Node lnk)
    {
        next = lnk;
    }

    // Returns the value in this node
    public int getInfo()
    {
        return info;
    }

    // Returns the link to the next node
    public Node getNext()
    {
        return next;
    }
}
}

public class Lab2B2
{
public static void main(String args[])
{
    Bag intBag = new Bag();

    for (int i =0; i < 10; i++)
    {
        int info = (int)(Math.random()*10);
        intBag.add(info);
    }

    // Before List
    System.out.print("List creation before: " + intBag);

    // Counts the # of occurrences of item in the bag

    //System.out.println("\nCount the number of occurrences:");
    //for(int i = 0; i <= 10; i++) 
    //{
    //System.out.println("Item " + i + " count = " + list.count(i));
    //}

    // Returns the number of items in the bag
    System.out.print("\nLength of List: " + intBag.getLength());

    // Adds an item to the bag
    intBag.add(9);
    System.out.print("\nList creation - Add(9):  " + intBag);

    // Removes an item from the bag, all occurrences of item in the bag
    intBag.remove(8);
    System.out.print("\nList creation - Remove(8):  " + intBag);

    // Removes all of the items from the bag
    intBag.clear();
    System.out.print("\nList creation - Clear():  " + intBag);

    // Determines whether the bag is empty

}
}

Upvotes: 0

Views: 198

Answers (2)

user890904
user890904

Reputation:

you are managing a LinkedList. what you need to do is run over the nodes and check if any of them equals the item you are checking for. in that case, you increase the count. the code is full of examples how to traverse the list. The method getLength() is a very good start as it has code that traverses all the elements. with minor modifications, you get what you want.

public int count(int item) {
    int count = 0;
    Node current = first.getNext();
    while (current != null)
    {
        if (current.getInfo()==item) {
          count++;
        }
        current = current.getNext();
    }
    return count;
}

Upvotes: 2

Paul Samsotha
Paul Samsotha

Reputation: 209072

Shouldn't you pass an int[] bag as an argument also, since there is no int[] bag declared as a class member?

public int count(int item, int[] bag) { 
    int count = 0;

    for(int i = 0; i < length; i++) {
        if(bag[i] == item) {
            count++;
        }
    }
    return count;
}

Upvotes: 1

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