Homework 1

Fall 2001

Due in class, Wednesday., Sep 12

2 points

This homework is designed to get you thinking about algorithms.

- Hoya Pizza sells a 9" square pizza with one topping for
$9.99, and Saxa Pizza sells an 10" round pizza with one topping
for $8.99. Which is the better buy?
- An algorithm is just a step-by-step procedure for accomplishing
a task. The steps you took above constitutes an algorithm, albeit
a very specific algorithm. A limitation is that it only works
for 9" square pizzas that cost $9.99 and for 10" round pizzas that
cost $8.99. Instead of using the actual numbers provided, rewrite
your previous ``algorithm'' using variables or symbols that represent
the numbers. For example, instead of writing 9.99, write roundPizzaCost,
and instead of writing 10, write roundPizzaSize.
For example, if we had a triangle pizza, we may write something like:

- trianglePizzaCost = 7.99
- trianglePizzaBase = 6
- trianglePizzaHeight = 9
- trianglePizzaArea = 0.5 x trianglePizzaBase x trianglePizzaHeight
- trianglePriceSqIn = trianglePizzaCost / trianglePizzaArea

The advantage of doing this is that we've separated the procedure for calculating the price per square inch of a pizza from any set of specific numbers. To compute a new price per square inch, we simply reassign the variables that correspond to the cost and the size of the pizza, and apply the algorithm.

- Assume that you are restricted to four actions: INPUT, CALCULATE,
DECISION, and OUTPUT. Express your algorithm for deciding which pizza
is the better buy in terms of these actions.
For our triangle pizza example, we may write something like:

- INPUT trianglePizzaCost
- INPUT trianglePizzaBase
- INPUT trianglePizzaHeight
- CALCULATE trianglePizzaArea = 0.5 x trianglePizzaBase x trianglePizzaHeight
- CALCULATE trianglePriceSqIn = trianglePizzaCost / trianglePizzaArea
- OUTPUT trianglePriceSqIn

- Draw a flowchart for Question 3's solution.
- On page 42, the authors present Euclid's algorithm for computing
the greatest common divisor (GCD) of two integers. Use the algorithm to
calculate the GCD of
*m*= 17 and*n*= 3. - Draw a flowchart for Euclid's algorithm.