Java 计数功能不起作用。控制台应用程序数字数组

Question

我的 int count(int i) 函数遇到问题:该函数应该计算列表中出现的数字的次数。例如有一个数字数组 3 4 4 1 3 2 1这是它应该显示的内容:

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

}
}

Answer 1

您正在管理一个 LinkedList。您需要做的是运行节点并检查它们是否等于您正在检查的项目。在这种情况下，您可以增加计数。该代码充满了如何遍历列表的示例。getLength() 方法是一个非常好的开始，因为它具有遍历所有元素的代码。只需稍加修改，您就可以得到您想要的。

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;
}