Inital commitHEADmaster

1 files changed, 190 insertions, 0 deletions

diff --git a/labs/lab03_dll/DLinkedList.java b/labs/lab03_dll/DLinkedList.java
new file mode 100644
index 0000000..ef0f495
--- /dev/null
+++ b/labs/lab03_dll/DLinkedList.java
@@ -0,0 +1,190 @@
+
+public class DLinkedList<T>
+{
+	private Node firstNode;
+	private Node lastNode;
+	private Node middleNode;
+	private int numberOfEntries;
+	private int middlePosition;
+	
+	public DLinkedList()
+	{
+		firstNode = null;
+		lastNode = null;
+		middleNode = null;
+		numberOfEntries = 0;
+		middlePosition = 0;
+	}
+	
+	public void add(T newEntry)
+	{
+		if(firstNode == null)
+		{
+			firstNode = new Node(null, newEntry, null);
+			lastNode = firstNode;
+		}
+		else
+		{
+			Node newNode = new Node(lastNode, newEntry, null);
+			lastNode.next = newNode;
+			lastNode = newNode;
+		}
+		
+		numberOfEntries++;
+		
+		if(numberOfEntries % 2 == 1)
+		{
+			if(middleNode == null)
+			{
+				middleNode = firstNode;
+			}
+			else
+			{
+				middleNode = middleNode.next;
+			}
+			middlePosition++;
+		}
+	}
+	
+	public T getEntry(int givenPosition)
+	{
+		T result = null;
+		
+		if((givenPosition >= 1) && (givenPosition <= numberOfEntries))
+		{
+			result = (getNodeAt(givenPosition)).data;
+		}
+		
+		return result;
+	}
+	
+	private Node getNodeAt(int givenPosition)
+	{
+		Node currentNode = firstNode;
+		
+		for(int counter = 1; counter < givenPosition; counter++)
+		{
+			currentNode = currentNode.next;
+		}
+		
+		return currentNode;
+	}
+	
+	public T getEntry1(int givenPosition)
+	{
+		T result = null;
+		
+		if((givenPosition >= 1) && (givenPosition <= numberOfEntries))
+		{
+			result = (getNodeAt1(givenPosition)).data;
+		}
+		
+		return result;
+	}
+	
+	/**
+	 * Modify this method according to the Solution 1
+	 */
+	private Node getNodeAt1(int givenPosition)
+	{
+		if(givenPosition > middlePosition)
+		{
+			//start from end, go backwars
+			Node temp = lastNode;
+			for(int i = 0;i<numberOfEntries - givenPosition;i++)
+			{
+				temp = temp.previous;
+			}
+			return temp;
+		}
+		else
+		{
+			//start from front, forwards
+			Node temp = firstNode;
+			for(int i = 1; i < givenPosition;i++)
+			{
+				temp = temp.next;
+			}
+			return temp;
+		}
+	}
+
+	public T getEntry2(int givenPosition)
+	{
+		T result = null;
+		
+		if((givenPosition >= 1) && (givenPosition <= numberOfEntries))
+		{
+			result = (getNodeAt2(givenPosition)).data;
+		}
+		
+		return result;
+	}
+	
+	/**
+	 * Modify this method according to the Solution 2
+	 */
+	private Node getNodeAt2(int givenPosition)
+	{
+		if(givenPosition < middlePosition)
+		{
+			if(givenPosition < middlePosition/2)
+			{
+				//STart from the front, go forwards
+				Node temp = firstNode;
+				for(int i = 1;i < givenPosition;i++)
+				{
+					temp = temp.next;
+				}
+				return temp;
+			}
+			else
+			{
+				//Start from the middle, backwards
+				Node temp = middleNode;
+				for(int i = middlePosition; i > givenPosition;i--)
+				{
+					temp = temp.previous;
+				}
+				return temp;
+			}
+		}
+		else
+		{
+			if(givenPosition < numberOfEntries*(3.0/4))
+			{
+				//Start from the middle, go forwards
+				Node temp = middleNode;
+				for(int i = middlePosition; i < givenPosition; i++)
+				{
+					temp = temp.next;
+				}
+				return temp;
+			}
+			else
+			{
+				//Start from the end, go backwards
+				Node temp = lastNode;
+				for(int i = numberOfEntries; i >givenPosition; i--)
+				{
+					temp = temp.previous;
+				}
+				return temp;
+			}
+		}
+	}
+	
+	private class Node
+	{
+		private Node previous;
+		private T data;
+		private Node next;
+		
+		private Node(Node previousNode, T aData, Node nextNode)
+		{
+			previous = previousNode;
+			data = aData;
+			next = nextNode;
+		}
+	}
+}