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/**
* Copyright © 2014 Mattias Andrée (maandree@member.fsf.org)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package datastructures.linkedlists;
/**
* Singly linked list class. A linked list is a
* list constructed from nodes, which hold stored
* values, with references to each other, this is
* usally an ineffective data structure, especially
* on high-level object orientated languages. A
* singly linked list only stores nodes with
* references to the following node. It also stores
* two refence nodes, the first node in the list,
* and the last node in the list. The implemention
* only implements methods that do not require
* iterating over all nodes for find a specific;
* all other methods' — those that are implemented
* — time complexity is Θ(1).
*
* @param <T> The value stored in the structure
*/
public class SinglyLinkedList<T>
{
/**
* Node for the list
*/
public class Node
{
/**
* Constructor
*
* @param value The value to store in the list
*/
private Node(T value)
{
this.value = value;
}
/**
* The value stored in the list by this node
*/
public T value;
/**
* The next node in the list
*/
public Node next = null;
}
/**
* The first node in the list
*/
public Node head = null;
/**
* The last node in the list
*/
public Node tail = null;
/**
* Insert a value in the beginning of the list
*
* @param value The value to insert
* @return The node that has be created and inserted
*/
public Node insertBeginning(T value)
{
Node node = new Node(value);
node.next = this.head;
if (this.head == null)
this.tail = node;
this.head = node;
return node;
}
/**
* Remove the node at the beginning of the list
*
* @return The node that has been removed
*/
public Node removeBeginning()
{
Node node = head;
if (node != null)
head = head.next;
if (this.tail == node)
this.tail = null;
return node;
}
/**
* Insert a value after a specified, reference, node
*
* @param value The value to insert
* @param predecessor The reference node
* @return The node that has be created and inserted
*/
public Node insertAfter(T value, Node predecessor)
{
Node node = new Node(value);
node.next = predecessor.next;
predecessor.next = node;
if (this.tail == predecessor)
this.tail = node;
return node;
}
/**
* Remove the node after a specified, reference, node
*
* @param predecessor The reference node
* @return The node that has been removed
*/
public Node removeAfter(Node predecessor)
{
Node node = predecessor.next;
if (node == null)
predecessor.next = node.next;
if (this.tail == node)
this.tail = predecessor;
return node;
}
/**
* Insert a value in the end of the list
*
* @param value The value to insert
* @return The node that has be created and inserted
*/
public Node insertEnd(T value)
{
if (this.tail == null)
return insertBeginning(value);
return insertAfter(value, this.tail);
}
}
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