CIS 200 Final Review

1. CIS 200 Final Review

2. New Material

3. Sorting

4. Selection Sort • Repeated scan of list for smallest/largest value • Each swap with item in correct spot • Big O, N-1 Passes • Probes – O(N^2) • Data Movements – O(N)

5. Insertion Sort • Like cards being one at a time • Array is split into 2 logical parts, sorted and unsorted • On each pass, next item from unsorted walks (via swaps) to correct position in sorted portion • Big O, N-1 passes Best, Worst, Ave. cases • Best – O(N) • Worst – O(N^2), T(N) =1/2N^2 – 1/2N • Avg – O(N^2), T(N) = 1/4N^2…

6. Merge Sort Recursive • Divide list into 2 parts • Sort each part using recursion • Combine the 2 (now sorted) parts into one sorted list Big O • Best, Avg, Worst – O(N log2 N)

7. Quick Sort • Partition is the key Two approaches • Dr. Wright’s • Text, from E18.10, p. 745 Big O • Worst case is when pivot is extreme value (min or max) • Already sorted list! • O(N^2) • Best/Avg • O(N log2 N) • Really is twice as fast as merge sort on average

8. Data Structures

9. Linked List

10. Doubly Linked List

11. Doubly Linked List

12. Doubly Linked List

13. Queue

14. Queue

15. Stack

16. Stack

17. Binary Search Tree • How to add items • Show a well-balanced BST – Add in this order: 9, 7, 12, 15, 2 • Show a poorly balanced BST – Add in this order: 2, 7, 9, 12, 15 • How to search • Show Inorder traversal in BST

18. Traversals • Preorder • Inorder • Postorder http://www.cs.cmu.edu/~adamchik/15-121/lectures/Trees/trees.html

19. Generics • Generic methods • Generic classes

20. .NET Collections • Esp. Hash Table • Collisions • Bucket – Linked List • Load Factor

21. Test 01 Material

22. Memory Management • C, C++ - Have to “allocate” memory • Forgetting to “free” results in memory leaks • “Garbage Collector” Rounds up and “reclaims” memory • Variables that drop out of “scope” will be collected • Temporary values inside methods reclaimed on method exit • Generally uncontrolled by the developer

23. LINQLanguage Integrated Query • Perform Queries Against Objects, Data

24. LINQ Keywords • “from” - Data Source • “where” – Filters the source elements with Boolean expressions • “select” – Choosing the data type to work with • “group” – Groups results according to a desired key value • “orderby” – Sorts the query results in ascending or descending order based on a comparer • “let” – Introduce a variable for query use • Select new creates anonymous class as result set

26. Namespaces, Scope Classes, often with common functionality, bundled together • System.Console • System.Collections.Generic • System.Linq Scope • “private” – Can only be accessed by the class, object itself • “protected” – Can only be accessed by the class, object, or any child classes, objects • “public” – Available access for all

27. Constructors C#, .NET compiler provides a ‘free’ constructor - Default • No parameters • When a new constructor is created, ‘free’ constructor goes away • Constructors can be “connected” with “this”

29. Interfaces • Object used for creating “interfaces”, common code • Classes “implement” an interface • All methods, properties are “abstract” in an interface • Objects that implement interface can be grouped • List<IPayable> • IPayable, IDisposable, etc

31. Inheritance • Classes with child or children classes • Can be used to “share” common code properties • Allows for “unique” objects, while reducing code • Object -> Person -> Student • Object -> Person -> Employee

32. Polymorphism • Override • Virtual • abstract

33. Inheritance - Keywords • “abstract” – Methods marked MUST be overridden • Class declared with abstract prevents creation with “new” • “virtual” – Methods marked CAN be overridden • Controls “how” other classes inherit information from the class • Private, protected, public – Used to control what is inheritance

36. Casting • Convert one type to another • Integer to String • Decimal to Integer • Byte to Integer • C#, .NET will know how to “box” and “unbox” types • Decimal -> Object -> Integer • Remember back to the Person – Student relationship • We can “cast” Person to Student both ways

37. Will cast to student just fine Will compile, But will throw an EXCEPTION at runtime

38. Exceptions and Exception Handling • Exceptions are… • “Exceptional” events • Unexpected events, errors during runtime • Unhandled exceptions? Stack trace and application death • Handled with try/catch/finally blocks • Try block “attempts” to run the code in question • Catch block handles the exception(s) that may occur • Finally block, optional, always executes

41. Vs. multiple catches • What order must the catch clauses appear?

42. Test 02 Material

43. Windows Forms, GUI Programming • Elements • Textboxes • Tab Groups • Checkboxes • Fields • Menus • Combobox • Event Handlers • Visual Studio Designer

44. Event Handlers • “Events” triggered by end user • Button Press • Key Press • Field Entry • …other GUI modifications or events

45. Role of Delegates in Event Handling • Sender? • E? • Need examples

46. Files and Streams • Files • Objects on Disks • Streams • Data structure that exposes • Read • Write • Synchronous • Asynchronous

47. Write to File

48. Read from File

49. Recursion …a solution strategy that involves a simpler version of the same problem. The problem becomes simplified with each call until we reach a stopping point. Resolution level by level. Useful for • Complex equations (Fibonacci number) • Towers of Hanoi • Binary Searching • Entry point • Stopping point • Deceptively simple

50. Define a Recursion Method What is my base case? • What is the solution to my base case? What is my intermediate case? • What is the solution to the intermediate case?