Question

Part 3 (20 points). This part is a practice of designing and implementing a recursive method. The recursive method to be impl

Here is the IntegerLinkedList_incomplete class:

public class IntegerLinkedList {

        static class Node {

            /** The element stored at this node */
            private int element;            // reference to the element stored at this node

            /** A reference to the subsequent node in the list */
            private Node next;         // reference to the subsequent node in the list

            /**
             * Creates a node with the given element and next node.
             *
             * @param e  the element to be stored
             * @param n  reference to a node that should follow the new node
             */
            public Node(int e, Node n) {
              element = e;
              next = n;
            }

            // Accessor methods
            /**
             * Returns the element stored at the node.
             * @return the element stored at the node
             */
            public int getElement() { return element; }

            /**
             * Returns the node that follows this one (or null if no such node).
             * @return the following node
             */
            public Node getNext() { return next; }

            // Modifier methods
            /**
             * Sets the node's next reference to point to Node n.
             * @param n    the node that should follow this one
             */
            public void setNext(Node n) { next = n; }
          } //----------- end of nested Node class -----------

          // instance variables of the SinglyLinkedList
          /** The head node of the list */
          private Node head = null;               // head node of the list (or null if empty)

          /** The last node of the list */
          private Node tail = null;               // last node of the list (or null if empty)

          /** Number of nodes in the list */
          private int size = 0;                      // number of nodes in the list
          
          public Node getHead() { return head; }
          public Node getTail() { return tail; }
          public int getSize() { return size; }
          
          public void setHead(Node h) { head = h; }
          public void setTail(Node t) { tail = t; }
          public void setSize(int s) { size = s; }
          
          /** Constructs an initially empty list. */
          public IntegerLinkedList() { }              // constructs an initially empty list

          // access methods
          /**
           * Returns the number of elements in the linked list.
           * @return number of elements in the linked list
           */
          public int size() { return size; }

          /**
           * Tests whether the linked list is empty.
           * @return true if the linked list is empty, false otherwise
           */
          public boolean isEmpty() { return size == 0; }

          /**
           * Returns (but does not remove) the first element of the list
           * @return element at the front of the list (or -1000000 if empty)
           */
          public int first() {             // returns (but does not remove) the first element
            if (isEmpty()) return -1000000;
            return head.getElement();
          }

          /**
           * Returns (but does not remove) the last element of the list.
           * @return element at the end of the list (or -1000000 if empty)
           */
          public int last() {              // returns (but does not remove) the last element
            if (isEmpty()) return -1000000;
            return tail.getElement();
          }

          // update methods
          /**
           * Adds an element to the front of the list.
           * @param e  the new element to add
           */
          public void addFirst(int e) {                // adds element e to the front of the list
            head = new Node(e, head);              // create and link a new node
            if (size == 0)
              tail = head;                           // special case: new node becomes tail also
            size++;
          }

          /**
           * Adds an element to the end of the list.
           * @param e  the new element to add
           */
          public void addLast(int e) {                 // adds element e to the end of the list
            Node newest = new Node(e, null);    // node will eventually be the tail
            if (isEmpty())
              head = newest;                         // special case: previously empty list
            else
              tail.setNext(newest);                  // new node after existing tail
            tail = newest;                           // new node becomes the tail
            size++;
          }

          /**
           * Removes and returns the first element of the list.
           * @return the removed element (or -1000000 if empty)
           */
          public int removeFirst() {                   // removes and returns the first element
            if (isEmpty()) return -1000000;              // nothing to remove
            int answer = head.getElement();
            head = head.getNext();                   // will become null if list had only one node
            size--;
            if (size == 0)
              tail = null;                           // special case as list is now empty
            return answer;
          }
          
          /**
           * Removes the node pointed to by r
           * @param r: pointer to the node to be removed
           * @return: the int element of the removed node
           */
          public int removeNode(Node r) {
                  if (isEmpty()) return -1000000;
                  Node current = head;
                  Node previous = current;
                  while ((current != null) && (current != r)) {
                          previous = current;
                          current = current.getNext();
                  }
                  if (current == null) return -1000000;
                  previous.next = current.getNext();
                  size--;
                  if (size == 0)
                      tail = null;
                  return current.getElement();
          }
          
          /**
           * Prints the elements in the given linked list
           * @param head: head of a linked list
           */
          public static void printList(Node head) {
                  Node current = head;
                  while (current != null) {
                          System.out.print(current.getElement() + "  ");
                          current = current.getNext();
                  }
          }
          
          public IntegerLinkedList copyList()  {
          
            IntegerLinkedList other = new IntegerLinkedList(); 
            if (size > 0) {                    // we need independent chain of nodes
              other.head = new Node(head.getElement(), null);
              int s = other.getSize();
              s++;
              other.setSize(s);
              Node walk = head.getNext();      // walk through remainder of original list
              Node otherTail = other.head;     // remember most recently created node
              while (walk != null) {              // make a new node storing same element
                Node newest = new Node(walk.getElement(), null);
                otherTail.setNext(newest);     // link previous node to this one
                s = other.getSize();
                    s++;
                    other.setSize(s);
                otherTail = newest;
                walk = walk.getNext();
              }
            }
            return other;
          }
          
          /**
           * Reverses the order of first n elements in the give linked list recursively
           * @param list: IntegerLinkedList 
           * @param n: 1 <= n <= size of the list
           * @return: a Node type; exactly what should be returned (or nothing is returned) must be determined by students 
           * in the context of their recursive algorithm; refer to the assignment
           */
          public static Node reverseFirstN(IntegerLinkedList list, int n) {
                
                // complete this method
                // this method must be a recursive method
                
          }
          
}

Here is the Hw4_Part3 class:

public class Hw4_Part3 {
        
        public static void main(String[] args) {

                IntegerLinkedList intList = new IntegerLinkedList();
                
                for (int i=1; i<=10; i++) {
                        intList.addLast(i*10);
                }
                
                System.out.println("Original list: ");
                IntegerLinkedList.printList(intList.getHead());
                System.out.println();
                
                // make a copy and use it for testing
                IntegerLinkedList intListCopy = new IntegerLinkedList();
                intListCopy = intList.copyList();
                
                int N = 2;
                IntegerLinkedList.reverseFirstN(intListCopy, N);
                System.out.println("\nAfter reversing first " + N + " elements: ");
                IntegerLinkedList.printList(intListCopy.getHead());
                System.out.println();
                
                intListCopy = intList.copyList();
                N = 4;
                IntegerLinkedList.reverseFirstN(intListCopy, N);
                System.out.println("\nAfter reversing first " + N + " elements: ");
                IntegerLinkedList.printList(intListCopy.getHead());
                System.out.println();
                
                intListCopy = intList.copyList();
                N = 8;
                IntegerLinkedList.reverseFirstN(intListCopy, N);
                System.out.println("\nAfter reversing first " + N + " elements: ");
                IntegerLinkedList.printList(intListCopy.getHead());
                System.out.println();

        }

}
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Answer #1
/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */




public class Hw4_Part3 {
        
        public static void main(String[] args) {

                IntegerLinkedList intList = new IntegerLinkedList();
                
                for (int i=1; i<=10; i++) {
                        intList.addLast(i*10);
                }
                
                System.out.println("Original list: ");
                IntegerLinkedList.printList(intList.getHead());
                System.out.println();
                
                // make a copy and use it for testing
                IntegerLinkedList intListCopy = new IntegerLinkedList();
                intListCopy = intList.copyList();
                
                int N = 2;
                IntegerLinkedList.reverseFirstN(intListCopy, N);
                System.out.println("\nAfter reversing first " + N + " elements: ");
                IntegerLinkedList.printList(intListCopy.getHead());
                System.out.println();
                
                intListCopy = intList.copyList();
                N = 4;
                IntegerLinkedList.reverseFirstN(intListCopy, N);
                System.out.println("\nAfter reversing first " + N + " elements: ");
                IntegerLinkedList.printList(intListCopy.getHead());
                System.out.println();
                
                intListCopy = intList.copyList();
                N = 8;
                IntegerLinkedList.reverseFirstN(intListCopy, N);
                System.out.println("\nAfter reversing first " + N + " elements: ");
                IntegerLinkedList.printList(intListCopy.getHead());
                System.out.println();

        }

}



public class IntegerLinkedList {

        static class Node {

            /** The element stored at this node */
            private int element;            // reference to the element stored at this node

            /** A reference to the subsequent node in the list */
            private Node next;         // reference to the subsequent node in the list

            /**
             * Creates a node with the given element and next node.
             *
             * @param e  the element to be stored
             * @param n  reference to a node that should follow the new node
             */
            public Node(int e, Node n) {
              element = e;
              next = n;
            }

            // Accessor methods
            /**
             * Returns the element stored at the node.
             * @return the element stored at the node
             */
            public int getElement() { return element; }

            /**
             * Returns the node that follows this one (or null if no such node).
             * @return the following node
             */
            public Node getNext() { return next; }

            // Modifier methods
            /**
             * Sets the node's next reference to point to Node n.
             * @param n    the node that should follow this one
             */
            public void setNext(Node n) { next = n; }
          } //----------- end of nested Node class -----------

          // instance variables of the SinglyLinkedList
          /** The head node of the list */
          private Node head = null;               // head node of the list (or null if empty)

          /** The last node of the list */
          private Node tail = null;               // last node of the list (or null if empty)

          /** Number of nodes in the list */
          private int size = 0;                      // number of nodes in the list
          
          public Node getHead() { return head; }
          public Node getTail() { return tail; }
          public int getSize() { return size; }
          
          public void setHead(Node h) { head = h; }
          public void setTail(Node t) { tail = t; }
          public void setSize(int s) { size = s; }
          
          /** Constructs an initially empty list. */
          public  IntegerLinkedList() { }              // constructs an initially empty list

          // access methods
          /**
           * Returns the number of elements in the linked list.
           * @return number of elements in the linked list
           */
          public int size() { return size; }

          /**
           * Tests whether the linked list is empty.
           * @return true if the linked list is empty, false otherwise
           */
          public boolean isEmpty() { return size == 0; }

          /**
           * Returns (but does not remove) the first element of the list
           * @return element at the front of the list (or -1000000 if empty)
           */
          public int first() {             // returns (but does not remove) the first element
            if (isEmpty()) return -1000000;
            return head.getElement();
          }

          /**
           * Returns (but does not remove) the last element of the list.
           * @return element at the end of the list (or -1000000 if empty)
           */
          public int last() {              // returns (but does not remove) the last element
            if (isEmpty()) return -1000000;
            return tail.getElement();
          }

          // update methods
          /**
           * Adds an element to the front of the list.
           * @param e  the new element to add
           */
          public void addFirst(int e) {                // adds element e to the front of the list
            head = new Node(e, head);              // create and link a new node
            if (size == 0)
              tail = head;                           // special case: new node becomes tail also
            size++;
          }

          /**
           * Adds an element to the end of the list.
           * @param e  the new element to add
           */
          public void addLast(int e) {                 // adds element e to the end of the list
            Node newest = new Node(e, null);    // node will eventually be the tail
            if (isEmpty())
              head = newest;                         // special case: previously empty list
            else
              tail.setNext(newest);                  // new node after existing tail
            tail = newest;                           // new node becomes the tail
            size++;
          }

          /**
           * Removes and returns the first element of the list.
           * @return the removed element (or -1000000 if empty)
           */
          public int removeFirst() {                   // removes and returns the first element
            if (isEmpty()) return -1000000;              // nothing to remove
            int answer = head.getElement();
            head = head.getNext();                   // will become null if list had only one node
            size--;
            if (size == 0)
              tail = null;                           // special case as list is now empty
            return answer;
          }
          
          /**
           * Removes the node pointed to by r
           * @param r: pointer to the node to be removed
           * @return: the int element of the removed node
           */
          public int removeNode(Node r) {
                  if (isEmpty()) return -1000000;
                  Node current = head;
                  Node previous = current;
                  while ((current != null) && (current != r)) {
                          previous = current;
                          current = current.getNext();
                  }
                  if (current == null) return -1000000;
                  previous.next = current.getNext();
                  size--;
                  if (size == 0)
                      tail = null;
                  return current.getElement();
          }
          
          /**
           * Prints the elements in the given linked list
           * @param head: head of a linked list
           */
          public static void printList(Node head) {
                  Node current = head;
                  while (current != null) {
                          System.out.print(current.getElement() + "  ");
                          current = current.getNext();
                  }
          }
          
          public IntegerLinkedList copyList()  {
          
            IntegerLinkedList other = new IntegerLinkedList(); 
            if (size > 0) {                    // we need independent chain of nodes
              other.head = new Node(head.getElement(), null);
              int s = other.getSize();
              s++;
              other.setSize(s);
              Node walk = head.getNext();      // walk through remainder of original list
              Node otherTail = other.head;     // remember most recently created node
              while (walk != null) {              // make a new node storing same element
                Node newest = new Node(walk.getElement(), null);
                otherTail.setNext(newest);     // link previous node to this one
                s = other.getSize();
                    s++;
                    other.setSize(s);
                otherTail = newest;
                walk = walk.getNext();
              }
            }
            return other;
          }
          
          /**
           * Reverses the order of first n elements in the give linked list recursively
           * @param list: IntegerLinkedList 
           * @param n: 1 <= n <= size of the list
           * @return: a Node type; exactly what should be returned (or nothing is returned) must be determined by students 
           * in the context of their recursive algorithm; refer to the assignment
           */
          public static void reverseFirstN(IntegerLinkedList list, int n) {
                
                // complete this method
                // this method must be a recursive method
                ///first travel till the element n 
                Node plusone;
               reverseFirstNutil(list.getHead(),plusone,n);
                   
                
          }
          public static void reverseFirstNutil(Node temp,Node plusone,int n){
                   
                   
                   if(n==1)
                   {    
                        plusone=temp.getNext();
                        Node headf=temp;
                        return;
                   }
                   reverseFirstNutil(temp.getNext(),plusone,n-1);
                   
                    Node q=temp.getNext();
                   q.next=temp;
                   temp.next=plusone;
                   // return headf;
               }
          
}

//here unable to rename file(.java). plz give correct direction

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