This is the presentation from class # 10 of the Logic and Problem-solving Course (on Arrays)

1. Class 10 – Arrays

2. Agenda
 Lateral Thinking Warm-up
 Project 1 Results, Issues
 Discussion: SAAD - Problem Solving with Code
 Discussion/Demo: Intro to Arrays
 Intro to Assignment 7: Daily Agenda
 Intro to Project 2: Battleship
 Task assignment
 Rubric
 Project Work and Wrap-up

3. System Analysis & Design
 Problem Solving with Code
 Tools
 IPO (outside in)
 Pseudocode (linear, integrative)
 Flowchart (linear, integrative)
 Models & Approaches
 SDLC
 3-tier (n-tier)
 MVC (OOP)

4. SAAD – 3-tier (n-tier)
 Presentation
 Logic
 Data

5. SAAD - MVC
 Model
 View
 Controller

6. MVVM – the NeXt Generation
 Model
 View
 View-Model
 Data Binding
 Service Structure

7. MVC, N-Tier, MVVM – who
cares?
 Moving towards OOP
 Clean division of work between functional
units
 Example: Calculator Converter: Model? View?
Controller?
 Project 2 – later tonight…

8. Intro to Arrays
 What is an array?
 A collection of related data
 Similar to a set of mailboxes at a site
 The site is the array, each mailbox represents an
element
 The mailbox may contain a specific value or object
 The contents can be strings, integers, or even
another array
 Addressed using brackets or parentheses (zero-
based)
 Can be examined iteratively or uniquely

9. Arrays Illustrated
 Single Dimension
 Array=days_of_week(7)
 2-Dimensional (table)
 Array=address_book(4,7)
Mon Tues Wed Thurs Fri Sat Sun
fname lname addr city prov post Email
joe smith 123 My Street Halifax NS B1B 1B1 joe@test.com
jane jones 1 Main Dr Dartmouth NS B7B 7B7 jane@mymail.com
pat white 21 Goode Dr. Halifax NS B1A 2C3 pat@hotmail.com
sam davis 19 Smith Dr. Timberlea NS B9G 2K8 sam@mailstop.com

10. Creating and Accessing Arrays
 Single Dimension
a = Array.new # an empty array
a = [] # same as above
puts a => nil (no output)
a[0]=“hello” # assigns the value
a[1]=“ world”
puts a[0] + a[1]
puts a
x = [1,”green”,”martian”]

11. Array Properties and Methods
 Properties
a=[“hello”, 1, “world”,2,”!”]
 a.last => “!”
 a.first => “hello”
 a[0].class => String
 a[1].class => Fixnum
 a.at(1) => 1
 a.length => 5

12. Array Properties and Methods
 Methods
a.push (“my friend”) => [ “hello”, 1,
“world”,2,”!”,”my friend”]
a.pop => [ “hello”, 1, “world”,2,”!”]
a.sort => [1,2, “!”,”hello”,”world”]
a.reverse = [“!”,2,”world”,1,”hello”]
a.sort! => applied to array (permanent change)
a.delete_at(2) => [ “hello”, 1, 2,”!”]
a.each do |variable|
end => iterates through the array

13. Creating and Accessing Arrays
 Practice
Handout: Exercise 10-1, Creating and
Accessing an Array

14. 2-Dimensional Arrays
 Creating
 x=Array.new(4) {Array.new(7)}
 a=[[1,"green"],[2,"red"],[3,"blue"]]
 Accessing & Assigning
 myval= a[1][0] => “green”
 x[2][4]=“Halifax”
 a[1][1]=“orange”

15. Iterating Through Arrays
 Using each
rows=5
cols=5
countr=0
mtrx=Array.new(rows) {Array.new(cols)}
mtrx.each do |myvar|
myvar.each do |ovar|
ovar=countr
countr=countr+1
end
end

16. Iterating Through Arrays
 Using for
rows=5
cols=5
countr=0
for x in (0..rows-1)
for y in (0..cols-1)
mtrx[x][y]=countr
countr=countr+1
end
end

17. Creating and Accessing Arrays
 Practice
Handout: Exercise 10-2, Creating and
Accessing a multi-dimensional
Array

18. Assignment 7: Daily Agenda
 Use a 2D Array to hold details
 Prompt for time (hour only)
 Prompt for appointment
 Prompt for location
 Assign inputs to elements
 Continue to prompt until user types in a blank
in the time slot
 Sort the Agenda and then generate Daily
Agenda by iterating through the array

19. Project 2: Battleship
 Simple Version
 8 x 8 grid (A-H, 1-8)
 2 ships each player
 Each ship assigned to a particular grid location
 10 shots each player
 A shot to the location of a vessel sinks it
 Draw grid and results after each shot
 “~” is unknown, “!” is sunk, “0” is a miss
 If two of the ships of any player are sunk, the other player
wins, end game
 If after ten shots one player has more ships than the other,
he/she wins, otherwise it’s a tie.

20. Wrap-up
 Summary
 Arrays
 Analysis & Design
 Assignment
 Project
 Next Week
 Brief intro to Classes
 Business Problems with Fishbone Diagram
 Project Time*

21. Practice/ Set-up
 Use this time to attempt the assignment to
prepare you for the project, OR
 Begin to set up your tasks, OR
 See me about any issues with grades, etc. OR
 Do any research you need to get the
assignment or project completed.
 GREAT TIP SITE:
 http://www.techotopia.com/index.php/Understanding_