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icalik/LinkedList.java

Created October 18, 2015 22:44
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LinkedList.java
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LinkedList.java
// doublyLinked.java
// demonstrates doubly-linked list
// to run this program: C>java DoublyLinkedApp
////////////////////////////////////////////////////////////////
class Link {
public long dData; // data item
public Link next; // next link in list
public Link previous; // previous link in list
// -------------------------------------------------------------
public Link(long d) // constructor
{
dData = d;
}
// -------------------------------------------------------------
public void displayLink() // display this link
{
System.out.print(dData + " ");
}
// -------------------------------------------------------------
} // end class Link
////////////////////////////////////////////////////////////////
class DoublyLinkedList {
private Link first; // ref to first item
private Link last; // ref to last item
// -------------------------------------------------------------
public DoublyLinkedList() // constructor
{
first = null; // no items on list yet
last = null;
}
// -------------------------------------------------------------
public boolean isEmpty() // true if no links
{
return first == null;
}
// -------------------------------------------------------------
public void insertFirst(long dd) // insert at front of list
{
Link newLink = new Link(dd); // make new link
if (isEmpty()) // if empty list,
last = newLink; // newLink <-- last
else
first.previous = newLink; // newLink <-- old first
newLink.next = first; // newLink --> old first
first = newLink; // first --> newLink
}
// -------------------------------------------------------------
public void insertLast(long dd) // insert at end of list
{
Link newLink = new Link(dd); // make new link
if (isEmpty()) // if empty list,
first = newLink; // first --> newLink
else {
last.next = newLink; // old last --> newLink
newLink.previous = last; // old last <-- newLink
}
last = newLink; // newLink <-- last
}
// -------------------------------------------------------------
public Link deleteFirst() // delete first link
{ // (assumes non-empty list)
Link temp = first;
if (first.next == null) // if only one item
last = null; // null <-- last
else
first.next.previous = null; // null <-- old next
first = first.next; // first --> old next
return temp;
}
// -------------------------------------------------------------
public Link deleteLast() // delete last link
{ // (assumes non-empty list)
Link temp = last;
if (first.next == null) // if only one item
first = null; // first --> null
else
last.previous.next = null; // old previous --> null
last = last.previous; // old previous <-- last
return temp;
}
// -------------------------------------------------------------
// insert dd just after key
public boolean insertAfter(long key, long dd) { // (assumes non-empty list)
Link current = first; // start at beginning
while (current.dData != key) // until match is found,
{
current = current.next; // move to next link
if (current == null)
return false; // didn't find it
}
Link newLink = new Link(dd); // make new link
if (current == last) // if last link,
{
newLink.next = null; // newLink --> null
last = newLink; // newLink <-- last
} else // not last link,
{
newLink.next = current.next; // newLink --> old next
// newLink <-- old next
current.next.previous = newLink;
}
newLink.previous = current; // old current <-- newLink
current.next = newLink; // old current --> newLink
return true; // found it, did insertion
}
// -------------------------------------------------------------
public Link deleteKey(long key) // delete item w/ given key
{ // (assumes non-empty list)
Link current = first; // start at beginning
while (current.dData != key) // until match is found,
{
current = current.next; // move to next link
if (current == null)
return null; // didn't find it
}
if (current == first) // found it; first item?
first = current.next; // first --> old next
else // not first
// old previous --> old next
current.previous.next = current.next;
if (current == last) // last item?
last = current.previous; // old previous <-- last
else // not last
// old previous <-- old next
current.next.previous = current.previous;
return current; // return value
}
// -------------------------------------------------------------
public void displayForward() {
System.out.print("List (first-->last): ");
Link current = first; // start at beginning
while (current != null) // until end of list,
{
current.displayLink(); // display data
current = current.next; // move to next link
}
System.out.println("");
}
// -------------------------------------------------------------
public void displayBackward() {
System.out.print("List (last-->first): ");
Link current = last; // start at end
while (current != null) // until start of list,
{
current.displayLink(); // display data
current = current.previous; // move to previous link
}
System.out.println("");
}
// -------------------------------------------------------------
} // end class DoublyLinkedList
////////////////////////////////////////////////////////////////
class LinkedList {
public static void main(String[] args) { // make a new list
DoublyLinkedList theList = new DoublyLinkedList();
theList.insertFirst(22); // insert at front
theList.insertFirst(44);
theList.insertFirst(66);
theList.insertLast(11); // insert at rear
theList.insertLast(33);
theList.insertLast(55);
theList.displayForward(); // display list forward
theList.displayBackward(); // display list backward
theList.deleteFirst(); // delete first item
theList.deleteLast(); // delete last item
theList.deleteKey(11); // delete item with key 11
theList.displayForward(); // display list forward
theList.insertAfter(22, 77); // insert 77 after 22
theList.insertAfter(33, 88); // insert 88 after 33
theList.displayForward(); // display list forward
} // end main()
} // end class DoublyLinkedApp
////////////////////////////////////////////////////////////////
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