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CSE142 Final
Winter 2011
Name of Student_______________________________________________________________
Section (e.g., AA)___________________ TA_____________________________________
This exam is divided into eleven questions with the following points:
# Problem Area Points Score
-----------------------------------------------------
1 Expressions 5 _____
2 Array Simulation 10 _____
3 Inheritance 6 _____
4 Token-Based File processing 10 _____
5 Line-Based File Processing 9 _____
6 Arrays 10 _____
7 ArrayList 10 _____
8 Critters 15 _____
9 Arrays 15 _____
10 Programming 10 _____
11 Art (bonus) 1 _____
----------------------------------
Total 100 _____
This is a closed-book/closed-note exam. You are allowed to have one
hand-written index card up to 5" x 8". Space is provided for your answers.
There is a "cheat sheet" at the end that you can use as scratch paper or to
write answers. You are not allowed to access any other paper during the exam
(not even scratch paper). Use the backs of the pages of this test if
necessary. Anyone caught with extra paper will lose at least 10 points.
In general the exam is not graded on style and you do not need to include
comments, although all fields of a class should be declared private. You do
not have to include any import statements. Do not abbreviate any code that you
write (e.g., S.o.p versus System.out.print) and do not abbreviate any answer
asking for sample output (show the complete output).
You are NOT to use any electronic devices while taking the test, including
calculators. Anyone caught using an electronic device will receive a 10 point
penalty.
Do not begin work on this exam until instructed to do so. Any student who
starts early or who continues to work after time is called will receive a 10
point penalty.
If you finish the exam early, please hand your exam to the instructor and exit
quietly through the front door.
1. Expressions, 5 points. For each expression in the left-hand column,
indicate its value in the right-hand column. Be sure to list a constant of
appropriate type (e.g., 7.0 rather than 7 for a double, Strings in quotes).
Expression Value
(6 + 7) / 4 / 2.0 __________
13 / 2 * 3 % 10 - 1 __________
30 / (2 * 6) + 1.5 __________
13 % 5 + 5 * 3 / 4 __________
"3 * 4" + 3 * 4 + 10 __________
2. Array Simulation, 10 points. You are to simulate the execution of a method
that manipulates an array of integers. Consider the following method:
public static void mystery(int[] list) {
for (int i = 1; i < list.length; i++) {
if (list[i - 1] % 2 == 0) {
list[i - 1]++;
list[i]++;
}
}
}
In the left-hand column below are specific lists of integers. You are to
indicate in the right-hand column what values would be stored in the list
after method mystery executes if the integer list in the left-hand column
is passed as a parameter to mystery.
Original List Final List
------------------------------------------------------------
[12, 7] ____________________________
[2, 3, 4, 5, 6] ____________________________
[3, 4, 5, 7, 9] ____________________________
[2, 3, 5, 7, 9] ____________________________
[4, 5, 9, 6, 2] ____________________________
3. Inheritance, 6 points. Assume the following classes have been defined:
public class A extends B {
public String toString() {
return "a";
}
}
public class B extends D {
public void method1() {
System.out.println("b 1");
}
public void method2() {
System.out.println("b 2");
}
}
public class C extends D {
public void method1() {
System.out.println("c 1");
}
}
public class D {
public String toString() {
return "d";
}
public void method1() {
System.out.println("d 1");
}
public void method2() {
System.out.println("d 2");
}
}
Consider the following code fragment:
D[] elements = {new B(), new A(), new D(), new C()};
for (int i = 0; i < elements.length; i++) {
System.out.println(elements[i]);
elements[i].method1();
elements[i].method2();
System.out.println();
}
What output is produced by this code? (you may write the output as a series
of 3-line columns in order from left to right)
4. Token-Based File Processing, 10 points. Write a static method called
showSums that takes as a parameter a Scanner containing a sequence of
integers and that reports each cumulative sum of the sequence and the
average of the numbers. For example, if the following text is stored in a
Scanner called data:
8 4 13 5 9
and we make the following call:
showSums(data);
your method should produce the following output:
Sum of 1 = 8
Sum of 2 = 12
Sum of 3 = 25
Sum of 4 = 30
Sum of 5 = 39
Average = 7.8
Notice that the various lines of output report the sum including just the
first number, then including the first two numbers, then including the first
three numbers, and so on, up to the sum including all numbers. The final
line of output reports the average of the sequence. Notice that this is the
average of the numbers themselves, not the average of the cumulative sums.
If the Scanner contains the following values:
1 2 3 4
the method should produce the following output:
Sum of 1 = 1
Sum of 2 = 3
Sum of 3 = 6
Sum of 4 = 10
Average = 2.5
You are to exactly reproduce the format of these sample outputs. You may
assume that the Scanner has at least one integer to be processed.
5. Line-Based File Processing, 9 points. Write a static method called
underline that takes a Scanner containing an input file as a parameter and
that prints to System.out the same text with certain lines underlined. The
lines to be underlined all begin with a period. The period should not be
printed. You should print the text that follows the period on a line by
itself followed by a line of dashes equal in length to the text that follows
the period. For example, consider the following input:
.Statement of Purpose
I didn't expect to major in computer science until I took cse142.
I liked it more than I expected and that got me hooked on cs.
.High School Performance
I got very good grades in high school, graduating in the top 10% of
my class.
.College Performance
I have done well in my college classes, with an overall gpa of 3.5.
If the text above is stored in a Scanner called input and we make this call:
underline(input);
the method should print the following output to System.out:
Statement of Purpose
--------------------
I didn't expect to major in computer science until I took cse142.
I liked it more than I expected and that got me hooked on cs.
High School Performance
-----------------------
I got very good grades in high school, graduating in the top 10% of
my class.
College Performance
-------------------
I have done well in my college classes, with an overall gpa of 3.5.
Notice that some of the input lines can be blank lines.
6. Arrays, 10 points. Write a static method called hasAlternatingParity that
returns whether or not an array of integers has alternating parity (true if
it does, false otherwise). The parity of an integer is 0 for even numbers
and 1 for odd numbers. To have alternating parity, a list would have to
alternate between even and odd numbers, as in the following list:
[3, 2, 19, 8, 43, 64, 1, 0, 3]
If these values are stored in an array called data and we make this call:
hasAlternatingParity(data)
the method would return true. If the array instead stored these values:
[2, 13, 4, 1, 0, 9, 2, 7, 4, 12, 3, 2]
it would return false because there are two even numbers in a row (4, 12).
By definition, an empty list or a list of one element has alternating
parity. You may assume the values in the array are not negative.
7. ArrayList, 10 points. Write a static method called switchPairs that
switches the order of values in an ArrayList of Strings in a pairwise
fashion. It should switch the order of the first two values, then switch
the order of the next two, switch the order of the next two, and so on.
For example, if a variable called list stores these values:
["four", "score", "and", "seven", "years", "ago"]
and we make this call:
switchPairs(list);
the method should switch the first pair ("four", "score"), the second pair
("and", "seven") and the third pair ("years", "ago"), yielding this list:
["score", "four", "seven", "and", "ago", "years"]
If there are an odd number of values in the list, the final element is not
moved. For example, if the original list had been:
["to", "be", "or", "not", "to", "be", "hamlet"]
It would again switch pairs of values, but the final value ("hamlet") would
not be moved, yielding this list:
["be", "to", "not", "or", "be", "to", "hamlet"]
8. Critters, 15 points. Write a class called Chameleon that extends the
Critter class. The instances of the Chameleon class cycle through three
different ways of displaying themselves. On their first move they should
appear as a red R. On their second move they should appear as a white W.
On their third move they should appear as a blue B. Then this pattern
repeats itself (red R, white W, blue B, red R, white W, blue B, etc). They
should always infect on moves when they are red no matter what is in front
of them. On moves when they are white or blue, they should hop when they
can and turn right when they can't hop.
9. Arrays, 15 points. Write a static method called doubleSize that takes an
array of integers as an argument and that returns a new array twice as large
as the original that replaces every integer from the original list with a
pair of integers, each half the original. If a number in the original list
is odd, then the first number in the new pair should be one higher than the
second so that the sum equals the original number. For example, if a
variable called list stores this sequence of values:
[18, 7, 4, 24, 11]
The number 18 is split into the pair (9, 9), the number 7 is split into (4,
3), the number 4 is split into (2, 2), the number 24 is split into (12, 12)
and the number 11 is stretched into (6, 5). Thus, the call:
int[] result = doubleSize(list);
should return an array containing this sequence:
[9, 9, 4, 3, 2, 2, 12, 12, 6, 5]
Your method should not change the array passed as a parameter. You are not
allowed to solve this problem using an ArrayList or Scanner and you are not
allowed to call any methods of the Arrays class or the Collections class.
10. Programming, 10 points. Write a static method called hasTwoPair that takes
an array of integers in the range of 1 to 6 as a parameter and that returns
whether or not the array contains two values that appear twice (true if it
does, false if it does not). This is a problem from the game of Yahtzee in
which players roll five dice and look for various combinations, but your
solution should not depend on the array containing five values. You can,
however, make use of the fact that all of the numbers will be in the range
of 1 to 6.
Your method should return true when exactly two values appearing in the
array occur exactly two times. If one value appears two times and another
appears three times, that would not count as two pairs. Similarly, if
there are three numbers that appear two times, that would not count as two
pairs. There must be exactly two such numbers and each must occur exactly
two times. Below are examples of arrays and the value that should be
returned for each by hasTwoPair:
Contents of array Value returned
------------------ --------------
{2, 4, 2, 2, 4} false
{3, 4, 3, 6, 6} true
{4, 1, 4, 4, 2} false
{5, 5, 3, 3, 4} true
{6, 2, 6, 5, 3} false
{1, 3, 5, 3, 1} true
{3, 1, 3, 1} true
{1, 2, 3, 1, 2, 3} false
11. Art, 1 point (bonus). You've programmed lions, bears, giants, and huskies,
but what kind of critter would your TA be? Give an artistic rendering of
how you see your TA fitting into the unforgiving world of the critter
simulation. You may either write a poem or draw a picture. If your answer
below indicates at least 1 minute of effort, you will receive full credit,
although your TA would probably appreciate it if you put in a little more
effort.
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Stuart Reges
Last modified: Fri Sep 16 16:07:22 PDT 2011