Understanding Algorithmic Processes: A Key to Problem Solving

1. LSP 121 Computers and Algorithmic Processes

2. What Is An Algorithmic Process? • An ordered series of steps that when applied to a problem produces a solution • Some call it “thinking logically” • Others refer to it simply as problem solving • Often simply called an algorithm

3. Why Should We Know What An Algorithmic Process Is? • Many things in life are algorithmic processes: Music, dance (such as ballet), art, biology (natural selection, nature), math, economics, daily living (buying a car or house, career changes, college choices) • Create useful short programs (called “macros”) in Access, Excel, and Word • E.g. Find all the grades for a student, remove the lowest homework grade, then calculate the average. • Write a simple program to analyze data and write the next article exposing cheaters in your school district (like Freakonomics)

4. Computers and Algorithms • Computers are very good at executing algorithms • But computers require precise instructions to perform an operation • This is basically the definition of an algorithm. (A series of precise instructions to perform an operation.) • The instructions cannot be ambiguous (must be clear and concise) • Let’s try an example – Begin today’s activity

5. What is an Algorithm? • Algorithms consist of four basic types of operations or instructions: 1. Sequential operations, e.g. Add 1 cup of butter; Subtract the amount of the check from the current account balance; Set the value of x to 1 2. Conditional operations, e.g. If the mixture is too dry, then add ½ cup water; If the current account balance < 0, then account overdrawn The if-else statement from today’s activity is an example of a conditional.

6. What is an Algorithm? 3. Iterative operations, e.g. Repeat the previous two steps until the mixture has thickened; Repeat the following five steps until there are no more checks to be processed; Repeat steps 1,2 and 3 until the value of y is equal to +1 ‘Looping’ as seen in today’s activity is an example of an iterative operation. 4. Calling a pre-existing algorithm (or function), e.g. Make a reduction with your sauce; date := getDate();

7. Algorithm to calculate Miles Per Gallon • Step 1: Get the values for gallons used, starting mileage, ending mileage • E.g. Ask the user to type in these values • Step 2: Set the value of distance driven to ending mileage – starting mileage • Step 3: Set the value of average miles per gallon to distance driven / gallons used • Step 4: Print the value of average miles per gallon • Step 5: Stop

8. “Fancier” Average Miles Per Gallon • Step 1: Get values for gallons used, starting mileage, ending mileage • Step 2: Set the value of distance driven to ending mileage – starting mileage • Step 3: Set the value of average miles per gallon to distance driven / gallons used • Step 4: Print the value of average miles per gallon (continued on next slide)

9. Modified Average Miles Per Gallon Continued • Step 5: If average miles per gallon is greater than 25.0 then • Print the message “You are getting good gas mileage!” Else • Print the message “You are NOT getting good gas mileage.” • Step 6: Stop

10. If-Else: e.g. Algorithm: Inviting Friends to a Party This slide is a demonstration of PESUDOCODE It is similar to programming statements, but are more English-like than programming-like. • Step 1: For each of your friends do this loop: • Step 2: • Ifthis a close friend then • Write an invitation • Address an envelope • Stick on a stamp • Else • Put their name on the reserve list • Step 3: Check off their name • Repeat Steps 2 and 3 until no more friends • Step 4: Count number of guests (for food) • Step 5: Mail invitations • Step 6: Stop

11. Let’s Try Another Example • Let’s try one together. Write an algorithm (in “pseudocode”) to examine student scores on an exam. You want to count how many students passed (>=70) and how many students failed (<70). When you hit the end of the list, print the total number of students that passed and the total number of students that failed. • Try next activity: Alice

12. Well-Known / Common Algorithms • Sorting data • Searching for data • Routing a packet across the Internet • Finding an optimal solution to a problem (such as finding the best route on a map using GPS device or mapping web site)

13. HTML • Hyper-Text Markup Language • All web pages are made (to varying degrees) from HTML • Relatively simple: no conditionals (if-else) or iterative statements (loops) • Each HTML command tells the web browser what to do next, such as start a new paragraph, display an image, or insert a hyperlink (clickable item)

14. <html> Begins every HTML document <head> Begins the head section <title>DePaul University </title> Title that appears on browser title bar </head> Ends the head section <body> Begins the body section This is the first line.<br> Text followed by line Break <p>Start a new paragraph.</p> Begins a new paragraph <h1>First Heading</h1> Level 1 heading (biggest) <h2>A second level heading</h2> Level 2 heading (little smaller) <hr> Inserts a horizontal rule (straight line) <strong>This line is bold.</strong> Bold text <br> <em>This line is italicized</em> Italicized text <br> <img src=“\images\banner.gif”> Insert an image here <a href=“http://www.cs.depaul.edu”> DePaul CS Page</a> Link to another web page </body> Close the body section </html> Ends every HTML document

15. Wanna learn how to create web pages? • CDM offers courses that teach you how: • IT-230: You also learn a little bit of programming • HCI-201: Uses FrontPage

16. HTML • Let’s try creating a web page using HTML Activity – Creating an e-portfolio

17. Last Activities • Let’s finish our algorithm topic with the following activities • Creating a Google Mash-up • VBA coin toss problem • If time permits – Google searching techniques