add sentinel doubly linked list

Signed-off-by: Mattias Andrée <maandree@operamail.com>

2 files changed, 51 insertions, 1 deletions

diff --git a/src/datastructures/linkedlists/SentinelDoublyLinkedList.java b/src/datastructures/linkedlists/SentinelDoublyLinkedList.java
new file mode 100644
index 0000000..11ab04a
--- /dev/null
+++ b/src/datastructures/linkedlists/SentinelDoublyLinkedList.java
@@ -0,0 +1,50 @@
+/**
+ * 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;
+
+
+/**
+ * Sentinel doubly 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 doubly linked list
+ * stores nodes with references to the both the
+ * following node previous node. A sentinel
+ * linked list increses performance and reduces
+ * complexity by tracking the edges implicitly
+ * rather than explicitly; instead of having
+ * reference to the first and last node, a
+ * sentinel linked list have an extra node,
+ * {@link #edge}, is placed at both the end and
+ * the beginning of the linked list — the list
+ * acts as linear but is constructed as circular
+ * — and rather than checking that the next node
+ * or previous node is not {@code null} you check
+ * that it is not {@link #edge}. This 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 SentinelDoublyLinkedList<T>
+£>export with_prev=1
+£>$GPP -s £ < src/datastructures/linkedlists/sentinel-template | sed -e '/^[/ ]\*/d'
+
diff --git a/src/datastructures/linkedlists/sentinel-template b/src/datastructures/linkedlists/sentinel-template
index 6d53ce5..43bebab 100644
--- a/src/datastructures/linkedlists/sentinel-template
+++ b/src/datastructures/linkedlists/sentinel-template
@@ -190,7 +190,7 @@
      */
     public Node removeEnd()
     {
-	return removeEnd(this.edge);
+	return removeBefore(this.edge);
     }
 £>fi