CS 260 – Exam I
September 21, 2012
Page 1 of 4
Name: _______KEY_____________________________
This exam is worth 100 points. There are questions totaling 130 points. You should omit questions
worth 30 points. If you do not leave some questions blank or otherwise mark which ones you want to
omit, I will quit grading when I have graded questions worth 100 points, so your last questions will not
be graded.
You may use additional paper from your instructor and staple it to your exam.
1. (20 points) Consider a class for the board game Jungle
(right), similar to the Stratego game. Draw a class diagram
for this class. Include at least 3 attributes and 3 methods
appropriate for this class. (If you include the constructor
method, you should have 4 methods.) If you like, your
attributes and methods can include playing the game
(moving pieces on the board, etc.) as well as the bare
essentials of the board. (You do not need to know how to play
the game to do this.)
Class Game Board
Board : Matrix or 2-D array
nRows, nCols : integer
(These are only examples …)
Constructor
Clear()
Initialize() (Set up starting positions)
MovePiece(row1,col1, row2, col2)
PrintBoard()
(Examples – could be others…)
2. (10 points) What does an iterator do? Why is it necessary to have an iterator, even when, for
example, the container ADT (such as a set) doesn’t have any order of elements?
The iterator gives access to all the elements of the container. It allows tests for membership (“Is x in
the container?”). It allows looping over all elements so you can calculate averages or find minimal
and maximal values, etc.
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CS 260 – Exam I
September 21, 2012
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3. (20 points) Assume that you are going to include a game board for the Jungle game program you
are writing, and that you will create an ADT for that game board. You need to pick out an
underlying data structure to use to build your game board. (For example, you might build your
board using a 1-D array, or a list of 1-D lists. Or you might build it using a set, or a dictionary, or a
matrix, or …). Pick two possible data structures you might use to build your ADT. (Call them
DS1 and DS2.) Then give at least two advantages of using one data structure over the other. (You
can give two advantages of DS1 over DS2, or one advantage of DS1 over DS2, along with one
advantage of DS2 over DS1.)
a. My DS 1: 1D list of 1D lists
These are only examples…
b. My DS 2: Matrix
c. Adv. 1: Matrix is better because …
d. Adv. 2: Matrix is better because …
4. (15 points) Why do we bother to develop and use Abstract Data Types (ADTs)? Lots of code has
been written without using ADTs. What advantage(s) do they provide to programmers who use
them?
ADTs allow us to pull together all the operations of a data object, while hiding the details of how it is
actually constructed. This information hiding is very important: It allows others using the ADT to
write their code without needing that knowledge, and it allows the ADT developers to go back in and
fix bugs or completely change the underlying data models without requiring any changes in the client
code.
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CS 260 – Exam I
September 21, 2012
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5. Assume that you need to create a new ADT for college courses like CS 150 and Math 125, for use
in a degree checker like DegreeWorks. (It could be used to answer questions like, “Has the student
passed all the courses required for the BS degree?”)
a. (20 points) Outline at least 4 of the basic attributes this ADT would need. (Name, data type,
and description or example values.)
Attribute name
Data type
Sentence description
Course name
String
“CS 150” or similar strings
Hours
Integer
1, 2, 3, … How many hours of credit?
Grade
String
Course grade: “A-” or “C+” or …
Semester
String or date
“Fall, 2012”
b. (20 points) Outline at least 4 methods that a “Course” ADT would need. (Name them,
including parameters and return values when necessary. Write a sentence or two telling what
each method does if it is not obvious from the name. The constructor is given as an example.)
Name, parameters, return value
Constructor(
,
,
,
Sentence description
)
Creates the “Course” object, setting the attributes to a default value.
CoursePassed()
Predicate: Did the student pass this course or not?
getGradePoints()
Return grade points (hours * grade points/hour, i.e., 4.0 for A, 3.0 for B)
Accessors & mutators for each
attribute…
8 possibilities…
checkValidity()
Is the course name in the UA catalog? Right number of hours? Etc.
c. (5 points) Draw a class
diagram including the
(Class) Course
These should match the attributes in part A.
attributes and methods
you outlined above.
Constructor
These should match the methods in part B.
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CS 260 – Exam I
September 21, 2012
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6. (10 points) Why is it important to have a constructor function? What does it do?
The constructor allocates the space in memory, and sets up everything with some initial values that
make sense for the ADT. This means that otherwise uninitialized integers will not have some really
strange values in the (negative) millions or billions, and other data members will also have reasonable
values.
7. In ADTs such as arrays and matrices, we had a method called __getitem__(self) and another
method called __setitem__(self, value).
a. (5 points) Explain why it was important in Python to use exactly these names. What
benefit did that give us?
Using these specific names (and other like them) allows Python to substitute
operators for the calls to these functions.
b. (5 points) Give an example of code that would call each of those
functions.
myArray[i] = 42
# calls __setitem__()
x = myArray[i]
# calls __getitem__()
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Exam points:
Q1
20
Q2
10
Q3
20
Q4
15
Q5
45
Q6
10
Q7
10
Total:
130
Points lost this page: ______