1. CS1S467 GUI Programming LECTURE 11 Collections

2. Lecture Slides are unsuitable for learning how to program!
You just get an illusion of learning!
Programming is a craft. You have to do it to learn it. 2

3. Review of Lab Session
Sorting arrays
Searching through arrays

4. Coursework 1 Deadline: Friday 15, 23:59, Blackboard Extra lab sessions
Read submission instructions
Read the marking grid (load/save highscore? Chart used? Finding max and min values, ...)
Don’t forget to include
testing document
installation documentation
game rules document
Extra lab sessions
Wednesday 6 and 13, 13:00 to 15:00 J210
No lecture next Monday

5. Today Overview Queues & Stacks what data structure to use when
What they are
methods
how to use
examples

6. Separating Boys from Men
Effective & appropriate use of data structures separates expert programmer from novice
The expert programmer recognises that:
organising data into appropriate data structures makes it easier to work with the data,
using data abstraction makes it easier to come up with a good solution to programming problems.

7. Collections vs. Primitive Data Types
Primitive Data Types: int, float, char, ….
not objects, can’t "do" things (sorting, searching)
simple to use, access and understand
"Hybrid": arrays and structs
"constructors", get & set methods
almost objects
Collections: List, ArrayList, LinkedList, Queues, Stacks, …
objects, can "do" things (sorting, searching)
more difficult to use, access and understand

8. Two Collection Groups Linear Indexed
Lists, LinkedLists, Queues, Stacks, etc.
fast sequential traverse
slow random access
Indexed
ArrayLists, SortedLists, etc.
slow sequential traverse
fast random access

9. Collections: Overview (When to use What)
Queue
Stack
LinkedList SortedList
List
ArrayList
Expand/shrink
Add/remove
fast
slow
Single use y
(y)
Sorting x
Depends on algorithm
Searching
Random access
Sequential access
Example
print queue
'Undo'
large data sorting
database
Guide on these and more Collections:

10. Queues & Stacks Stacks Queues
Last-in-First-out (LiFo): data added and removed only from top of list
used for
expression evaluation
function call handling
'Undo' functionality
Queues
First-in-First-out (FiFo): data are added at one end and removed from the other end of a list.
prioritise operating system processes
simulate events in the real world
batch processing

11. Basic Stack Methods Push & Pop Peek
just looking at topmost without removing

12. Other Stack Methods Clear Clone Contains CopyTo, ToArray
completely empties the Stack
Clone
creates a copy
Contains
checks if an element is in the Stack (sequentially -> slow)
CopyTo, ToArray
copies into a 1D array
Count (not a method, a property)
amount of elements on the Stack
Full list on:

13. How to Use the Stack Class
using System;
using System.Collections;
public class SamplesStack {
public static void Main()
// Creates and initializes a new Stack.
Stack myStack = new Stack();
myStack.Push("Hello");
myStack.Push("World");
myStack.Push("!");
// Displays the properties and values of the Stack. Console.WriteLine( "myStack" );
Console.WriteLine( "\tCount: {0}", myStack.Count ); Console.Write( "\tValues:" );
PrintValues( myStack ); }
public static void PrintValues( IEnumerable mS ) {
foreach ( Object obj in mS )
Console.Write( " {0}", obj ); }

14. Basic Queue Methods Enqueue & Dequeue Peek
just looking at first in queue without removing

15. Other Queue Methods (Identical to Stack)
Clear
completely empties the Queue
Clone
creates a copy
Contains
checks if an element is in the Queue (sequentially -> slow)
CopyTo, ToArray
copies into a 1D array
Count (not a method, a property)
returns amount of elements in the Queue
Full list on:

16. How to Use the Queue Class
using System;
using System.Collections;
public class SamplesQueue {
public static void Main()
// Creates and initializes a new Queue.
Queue myQ = new Queue();
myQ.Enqueue("Hello");
myQ.Enqueue("World");
myQ.Enqueue("!");
// Displays the properties and values of the Queue. Console.WriteLine( "myQ" );
Console.WriteLine( "\tCount: {0}", myQ.Count );
Console.Write( "\tValues:" );
PrintValues( myQ ); }
public static void PrintValues( IEnumerable mQ ) {
foreach ( Object obj in mQ )
Console.Write( " {0}", obj ); }

17. Example using System; using System.Collections;
public class Palindrome {
public static void Main()
bool isPalindrome=true;
string ch;
Stack myS = new Stack();
Console.WriteLine("Enter a word to check");
string wordToCheck = Console.ReadLine();
for (int x = 0; x < wordToCheck.Length; x++)
myS.Push(wordToCheck.Substring(x, 1)); }
int pos = 0;
while (myS.Count > 0)
ch = myS.Pop().ToString();
if (ch != wordToCheck.Substring(pos, 1))
isPalindrome = false;
break;
pos++;
Example
// Some variables we need
// Create and initialise a new Stack
// Ask user to enter a word to check
// Push the word onto the stack, letter by letter
// In effect the stack now holds the word BACKWARDS
// Now compare (letter by letter) the word entered
// to the reversed version on the Stack. If at any
// point the letters are different, then the word is
// not a palindrome.

18. Lists Lists are similar to arrays Either this way Or this way
Lists have to be given a size before use:
Either this way Or this way
(automatic run-time size-adjustment) (explicit size definition)

19. Lists Lists are also dissimilar to arrays
List are auto-initialised to zero
List are not fixed in size. They can grow at run-time

20. Lists Lists are objects
They have methods (already used the .Add() method)
Example: Searching

21. Lists Lists are objects
They have methods (already used the .Add() method)
Example: Sorting
Ah – and how to sort descending?

22. Lists Lists are objects
They have methods (already used the .Add() method)
Example: Inserting

23. Lists and structs Lists can store anything
int, double, float, char, .....
arrays
structs

24. Lists and structs Sorting a List of structs sort by what?
needs a sort definition

25. Lists and structs More after Christmas break
a 5 week project using Lists, structs and more visual components
a record (or whatever) collection / database
load, save, sort, search, ...

26. Reminder End of Lecture 11 Deadline: Friday 15, 23:59, Blackboard
Read submission instructions
Read the marking grid (load/save highscore? Chart used? Finding max and min values, ...)
Don’t forget to include
testing document
installation documentation
game rules document
Extra lab sessions
Wednesday 6 and 13, 13:00 to 15:00 J210
No lecture next Monday
End of Lecture 11