July First

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Containers & Generics

OA FakinledeUniversity of LagosMay 2011


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The Windows Forms Exercise of last week

allowed us to do some things with the Arraytype.

We used an array of Strings and we were ableto do the following:

Insert elements

Reverse Array Contents

Sort Array Contents

Display Current Contents

The Array Type


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As you have seen over the course of the

previous chapters, C# arrays allow you todefine a set of identically typed items(including an array of System.Objects, whichessentially represents an array of any types)

of a fixed upper limit.These could be Strings as our simple

examples show

They could be complex Objects as the

Student Class

Arrays & Generics?


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Arrays are limited by size which we must

state at the outset and cannot easily alterthereafter

Linear Data structures are implemented tosolve this problem and give the flexibility to

add new objects anywhere

A linear structure generalizes such conceptsas LIFO, FIFO and mixtures of these

It is automatically extensible

Arrays vs Lists


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Options for implementing an Generic List

Array has a fixed size

Data must be shifted during insertions anddeletions

Generic Linked list is able to grow in size asneeded

Does not require the shifting of items duringinsertions and deletions

Arrays vs Generic Lists


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Insertion into a List ofIntegers


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A reference contains the location, or address

in memory, of a memory cell Undefined Until The Next Object Exists

Initially Null

The Initialization Process Must Ensure this

points to some object May be trivial

Reference to the NextObject


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Deletion of a Node


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Delete First Node


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Size

Increasing the size of a resizable array canwaste storage and time

Storage requirements

Array-based implementations require lessmemory than a Linked lists

Arrays & Lists


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Access time

Array-based: constant access time

List-based: the time to access the ith nodedepends on i

Insertion and deletions

Array-based: require shifting of data

List-based: require a list traversal

These standard rules are only true in theory

because as we shall see, C Sharpim lementation allows a list to be converted

Compare


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Last node references the first node

Every node has a successor

No node in a circular linked list contains NULL

Singly Linked Circular List


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Double Link Circular List


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Inventory Items

Stacks of Cements Bags

Airline Queue

Locations of the seeds played in an Ayo Game

The University Bus Stop

Waiting For any service (Petrol Station, HostelWater, etc)

Examples


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The LinkedList generic class is located in

the Systems Generic namespace

LinkedList ) is a general-purposelinked list. It supports enumerators andimplements the ICollection interface,

consistent with other collection classes inthe .NET Framework.

Creation is very easy as, unlike when we usedan array, we need not specify the size.

Several properties and methods are given to

C Sharp Library Linked List


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The LinkedList Class implements the

ICollection and IEnumerable Interfaces ingeneric and non-generic forms.

ICollection allows us to easily convert thelinked list to an array, if necessary

IEnumerable allows us foreach iteration overeach contained item.

Linked List Class


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Public LinkedList();// non parametrized

constructor

public LinkedList(IEnumerable collection);

Allows another enumerable object such as apredefined array to initialize the linked list

Public int Count { get; }

// It can tell you how many items it contains

public LinkedListNode First { get; }

public LinkedListNode Last { get; }

LinkedList Methods andProperties


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public void AddAfter(LinkedListNode

node, LinkedListNode newNode)

public void AddBefore(LinkedListNodenode, LinkedListNode newNode);

public void AddFirst(LinkedListNodenode);

public void AddLast(LinkedListNodenode);

More Methods


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public void Clear();

public bool Contains(T value);

public void CopyTo(T[] array, int index); //starting from the index location

public LinkedListNode Find(T value);

public LinkedListNode FindLast(T value);

public LinkedList.EnumeratorGetEnumerator();

public void Remove(LinkedListNode

node);

More Methods


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// Create the link list.

string[] words = { "the", "fox", "jumped", "over", "the","dog" };

LinkedList sentence = newLinkedList(words);

Display(sentence, "The linked list values:");

Console.WriteLine("sentence.Contains(\"jumped\") ={0}",

sentence.Contains("jumped"));

A Simple Example


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// Move the first node to be the last node.LinkedListNode mark1 = sentence.First;

sentence.RemoveFirst();

sentence.AddLast(mark1);Display(sentence, "Test 2: Move first node to be

last node:");

// Change the last node be 'yesterday'.

Example Continued


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// Move the last node to be the first node.

mark1 = sentence.Last;

sentence.RemoveLast();

sentence.AddFirst(mark1);

Display(sentence, "Test 4: Move last node to befirst node:");

// Indicate, by using parentheisis, the lastoccurence of 'the'.

Example Continued


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// Add 'lazy' and 'old' after 'the' (the LinkedListNode

named current).

sentence.AddAfter(current, "old");

sentence.AddAfter(current, "lazy");

IndicateNode(current, "Test 6: Add 'lazy' and 'old'after 'the':");

// Indicate 'fox' node.

current = sentence.Find("fox");

" ' '

Example


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// Add 'quick' and 'brown' before 'fox':

sentence.AddBefore(current, "quick");

sentence.AddBefore(current, "brown");

IndicateNode(current, "Test 8: Add 'quick' and 'brown'

before 'fox':");

// Keep a reference to the current node, 'fox',

// and to the previous node in the list. Indicate the'dog' node.


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Console.WriteLine("Test 16: Copy the list to an array:");

// Create an array with the same number of

// elements as the inked list.

string[] sArray = new string[sentence.Count];

sentence.CopyTo(sArray, 0);


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LinkedList list = new

LinkedList();

int Current=0; // No longer necessary

Add to Partial Form1 Class


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Text = "A Simple I/O with Window Forms";

list.AddFirst("First Entry");

list.AddLast("Last Entry");

if (textBox1.Text == "")

button1.Enabled = false;

else

button1.Enabled = true;

Add to InitializeComponents


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list.AddFirst(textBox1.Text.ToString());

textBox1.Clear();

Current++; button1.Enabled = false;

button1.BackColor = Color.Aqua;

AddFirst


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Form1.ActiveForm.Text = "Last Item removed;

Click Display to see it";

list.RemoveLast();

RemoveLast()


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Pp 699-758 Bonus Material Chapter 21

HomeWork:

Ayo Game

Learn How it is played

Or Learn another game you can implementwith the data structures we have learned

Begin to define relevant classes

Forms Tutorial/HW


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Require your program to obtain a password

before starting. Let the password itself bemasked by dots or asterisks

Quiz

July First

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