Question

In Listing 5.2 (linkList2.java, Lafore book), the linked list is unordered. Modify the code so that the linked list is ordered, meaning that Link objects are linked in the ascending order of the key (iData). You need to add an insert() method, and change the find() and delete() methods to have the logic of processing the list in the ordered fashion. Please test your code a few sets of values.

Listing 5.2:

// linkList2.java
// demonstrates linked list
// to run this program: C>java LinkList2App
////////////////////////////////////////////////////////////////
class Link
{
public int iData; // data item (key)
public double dData; // data item
public Link next; // next link in list
// -------------------------------------------------------------
public Link(int id, double dd) // constructor
{
iData = id;
dData = dd;
}
// -------------------------------------------------------------
public void displayLink() // display ourself
{
System.out.print("{" + iData + ", " + dData + "} ");
}
} // end class Link
////////////////////////////////////////////////////////////////
class LinkList
{
private Link first; // ref to first link on list

// -------------------------------------------------------------
public LinkList() // constructor
{
first = null; // no links on list yet
}
// -------------------------------------------------------------
public void insertFirst(int id, double dd)
{ // make new link
Link newLink = new Link(id, dd);
newLink.next = first; // it points to old first link
first = newLink; // now first points to this
}
// -------------------------------------------------------------
public Link find(int key) // find link with given key
{ // (assumes non-empty list)
Link current = first; // start at 'first'
while(current.iData != key) // while no match,
{
if(current.next == null) // if end of list,
return null; // didn't find it
else // not end of list,
current = current.next; // go to next link
}
return current; // found it
}
// -------------------------------------------------------------
public Link delete(int key) // delete link with given key
{ // (assumes non-empty list)
Link current = first; // search for link
Link previous = first;
while(current.iData != key)
{
if(current.next == null)
return null; // didn't find it
else
{
previous = current; // go to next link
current = current.next;
}
} // found it
if(current == first) // if first link,
first = first.next; // change first
else // otherwise,
previous.next = current.next; // bypass it
return current;
}
// -------------------------------------------------------------
public void displayList() // display the list
{
System.out.print("List (first-->last): ");
Link current = first; // start at beginning of list
while(current != null) // until end of list,
{
current.displayLink(); // print data
current = current.next; // move to next link
}
System.out.println("");
}
// -------------------------------------------------------------
} // end class LinkList
////////////////////////////////////////////////////////////////
class LinkList2App
{
public static void main(String[] args)
{
LinkList theList = new LinkList(); // make list

theList.insertFirst(22, 2.99); // insert 4 items
theList.insertFirst(44, 4.99);
theList.insertFirst(66, 6.99);
theList.insertFirst(88, 8.99);

theList.displayList(); // display list

Link f = theList.find(44); // find item
if( f != null)
System.out.println("Found link with key " + f.iData);
else
System.out.println("Can't find link");

Link d = theList.delete(66); // delete item
if( d != null )
System.out.println("Deleted link with key " + d.iData);
else
System.out.println("Can't delete link");

theList.displayList(); // display list
} // end main()
} // end class LinkList2App
////////////////////////////////////////////////////////////////

Answer 1

please do upvote.If you have any problem do comment and i shall be happy to help you.Thanks for using HomeworkLib.

Note: changed/modified/added code is in bold

Note : you do not need to change anything in delete() and find() because they already process in ordered fashion

-------------------------------------------------------

// linkList2.java
// demonstrates linked list
// to run this program: C>java LinkList2App
////////////////////////////////////////////////////////////////
public class Link
{
public int iData; // data item (key)
public double dData; // data item
public Link next; // next link in list
// -------------------------------------------------------------
public Link(int id, double dd) // constructor
{
iData = id;
dData = dd;
}
// -------------------------------------------------------------
public void displayLink() // display ourself
{
System.out.print("{" + iData + ", " + dData + "} ");
}
} // end class Link
////////////////////////////////////////////////////////////////
class LinkList
{
private Link first; // ref to first link on list

// -------------------------------------------------------------
public LinkList() // constructor
{
first = null; // no links on list yet
}
// -------------------------------------------------------------
public void insertFirst(int id, double dd)
{ // make new link
Link newLink = new Link(id, dd);
newLink.next = first; // it points to old first link
first = newLink; // now first points to this
}

public void insert(int id,double dd)
{
   Link current;
   Link newLink = new Link(id, dd);

  
   //when list is empty
if (first == null || first.iData >= newLink.iData)
{
newLink.next = first;
first = newLink;
}
else {

  
  
current = first;

//traverse through the list to find the slot for newLink
while (current.next != null && current.next.iData < newLink.iData)
{
current = current.next;
}
newLink.next = current.next;
current.next = newLink;
}
}
// -------------------------------------------------------------
public Link find(int key) // find link with given key
{ // (assumes non-empty list)
Link current = first; // start at 'first'
while(current.iData != key) // while no match,
{
if(current.next == null) // if end of list,
return null; // didn't find it
else // not end of list,
current = current.next; // go to next link
}
return current; // found it
}
// -------------------------------------------------------------
public Link delete(int key) // delete link with given key
{ // (assumes non-empty list)
Link current = first; // search for link
Link previous = first;
while(current.iData != key)
{
if(current.next == null)
return null; // didn't find it
else
{
previous = current; // go to next link
current = current.next;
}
} // found it
if(current == first) // if first link,
first = first.next; // change first
else // otherwise,
previous.next = current.next; // bypass it
return current;
}
// -------------------------------------------------------------
public void displayList() // display the list
{
System.out.print("List (first-->last): ");
Link current = first; // start at beginning of list
while(current != null) // until end of list,
{
current.displayLink(); // print data
current = current.next; // move to next link
}
System.out.println("");
}
// -------------------------------------------------------------
} // end class LinkList
////////////////////////////////////////////////////////////////

-------------------------------------------------

public class OrderedList
{
public static void main(String[] args)
{
LinkList theList = new LinkList(); // make list

theList.insert(4, 2.99); // insert 4 items

theList.insert(1, 8.99);

theList.insert(2, 4.99);
theList.insert(3, 6.99);

theList.displayList(); // display list

Link f = theList.find(1); // find item
if( f != null)
System.out.println("Found link with key " + f.iData);
else
System.out.println("Can't find link");

Link d = theList.delete(2); // delete item
if( d != null )
System.out.println("Deleted link with key " + d.iData);
else
System.out.println("Can't delete link");

theList.displayList(); // display list
} // end main()
} // end class
////////////////////////////////////////////////////////////////

--------------------------