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CSE142A Final
Winter 2013
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. 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 the Critter class has special requirements you must follow.
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
17 / 3 + 55 % 20 / 2 __________
19.0 / 2 + 2 * 2.25 __________
2 + 2 + "." + 2 + 2 + 4 * 5 __________
73 / 10 * 4 / 3 / 2.0 * 3 __________
3 / 2 * (1.5 + 2.5) + 98 % 5 / 2 __________
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 = 2; i < list.length; i++) {
if (i % 2 == 0) {
list[i] = list[i] + list[i - 2];
}
}
}
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
------------------------------------------------------------
{2, 5, 8} ____________________________
{3, 4, 7, 5} ____________________________
{2, 4, 6, 2, 6} ____________________________
{4, 5, 8, 9, 3} ____________________________
{1, 2, 8, 5, 10, 5, 4} ____________________________
3. Inheritance, 6 points. Assume the following classes have been defined:
public class D extends C {
public void method1() {
System.out.println("d 1");
}
}
public class C {
public void method1() {
System.out.println("c 1");
}
public void method2() {
System.out.println("c 2");
}
public String toString() {
return "c";
}
}
public class A extends C {
public void method1() {
System.out.println("a 1");
}
public String toString() {
return "a";
}
}
public class B extends A {
public void method2() {
System.out.println("b 2");
}
}
Consider the following code fragment:
C[] elements = {new B(), new C(), new A(), new D()};
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? Write the output as a series of
3-line columns in order from left to right (do not label columns or rows).
4. Token-Based File Processing, 10 points. Write a static method called
printStrings that takes as a parameter a Scanner holding a sequence of
integer/String pairs and that prints to System.out one line of output for
each pair with the given String repeated the given number of times. For
example if the Scanner contains the following data:
6 fun. 3 hello 10 <> 4 wow!
your method should produce the following output:
fun.fun.fun.fun.fun.fun.
hellohellohello
<><><><><><><><><><>
wow!wow!wow!wow!
Notice that there is one line of output for each integer/String pair. The
first line has 6 occurrences of "fun.", the second line has 3 occurrences of
"hello", the third line has 10 occurrences of "<>" and the fourth line has 4
occurrences of "wow!". Notice that there are no extra spaces included in
the output. You are to exactly reproduce the format of this sample output.
You may assume that the input values always come in pairs with an integer
followed by a String. If the Scanner is empty (no integer/String pairs),
your method should produce no output.
5. Line-Based File Processing, 9 points. Write a static method called
flipLines that takes a Scanner containing an input file as a parameter and
that writes to System.out the same file with successive pairs of lines
reversed in order. For example, if the input file contains the following:
Twas brillig and the slithy toves
did gyre and gimble in the wabe.
All mimsey were the borogroves,
and the mome raths outgrabe.
"Beware the Jabberwock, my son,
the jaws that bite, the claws that catch,
Beware the JubJub bird and shun
the frumious bandersnatch."
The program should print the first pair of lines in reverse order, then the
second pair in reverse order, then the third pair in reverse order, and so
on. Thus, your method should produce the following output.
did gyre and gimble in the wabe.
Twas brillig and the slithy toves
and the mome raths outgrabe.
All mimsey were the borogroves,
"Beware the Jabberwock, my son,
Beware the JubJub bird and shun
the jaws that bite, the claws that catch,
the frumious bandersnatch."
Notice that a line can be blank, as in the third pair. Also notice that an
input file can have an odd number of lines, as in the one above, in which
case the last line is printed in its original position. You may not make
any assumptions about how many lines are in the Scanner.
6. Arrays, 10 points. Write a static method called minToFront that takes an
array of integers as a parameter and that moves the minimum value in the
list to the front by swapping its position with whatever is currently at the
front of the list. For example, if a variable called list stores the
following values:
[3, 8, 92, 4, 2, 17, 9]
and you make the following call:
minToFront(list);
The value 2 is the minimum, so the list should store the following values
after the call:
[2, 8, 92, 4, 3, 17, 9]
Notice that the value 3 which used to be at the front of the list is now at
index 4 where the value 2 was before. If there is more than one occurrence
of the minimum value, your method should move the first occurrence to the
front of the list. If the minimum value is already at the front of the
array or if the array is empty, then the array should be unchanged after the
method executes.
You may not construct any extra data structures to solve this problem (not
even a string).
7. ArrayList, 10 points. Write a static method called reverse3 that takes an
ArrayList of integer values as a parameter and that reverses each successive
sequence of three values in the list. For example, suppose that a variable
called list stores the following sequence of values:
[3, 8, 19, 42, 7, 26, 19, -8, 193, 204, 6, -4]
and we make the following call:
reverse3(list);
Afterwards the list should store the following sequence of values:
[19, 8, 3, 26, 7, 42, 193, -8, 19, -4, 6, 204]
The first sequence of three values (3, 8, 19) has been reversed to be (19,
8, 3). The second sequence of three values (42, 7, 26) has been reversed to
be (26, 7, 42). And so on. If the list has extra values that are not part
of a sequence of three, those values are unchanged. For example, if the
list had instead stored:
[3, 8, 19, 42, 7, 26, 19, -8, 193, 204, 6, -4, 99, 2]
The result would have been:
[19, 8, 3, 26, 7, 42, 193, -8, 19, -4, 6, 204, 99, 2]
Notice that the values (99, 2) are unchanged in position because they were
not part of a sequence of three values. You may not construct any extra
data structures to solve this problem. You must solve it by manipulating
the ArrayList you are passed as a parameter.
8. Critters, 15 points. Write a class called Raccoon that extends the Critter
class. The instances of the Raccoon class always infect when an enemy is in
front of them and otherwise randomly choose between turning left and turning
right, with each choice being equally likely. Their appearance changes over
time. Each Raccoon initially displays as a less-than followed by a dash
followed by a greater-than ("<->"). Then as each Raccoon chooses a move, it
changes its appearance to match that move. If its most recent move was an
infect, it displays as "<I>". If its most recent move was to turn left, it
displays as "<L>". And if its most recent move was to turn right, it
displays as "<R>". Its color should alternate between blue and red. It
should be blue initially when it is displayed as "<->" and then it should
alternate between the two colors (red after the first move, blue after the
second move, etc.).
As in assignment 8, all fields must be declared private and fields that need
to be initialized to a non-default value must be set in a constructor. If
you want to use a Random object, you should make it a field so that you only
construct it once for each Raccoon.
9. Arrays, 15 points. Write a static method called collapse that takes an
array of integers as a parameter and that returns a new array that contains
the result of collapsing the original list by replacing each successive pair
of integers with the sum of the pair. For example, if a variable called
list stores this sequence of values:
[7, 2, 8, 9, 4, 13, 7, 1, 9, 10]
Then the following call:
collapse(list)
Should return a new array containing the following values:
[9, 17, 17, 8, 19]
The first pair from the original list is collapsed into 9 (7 + 2), the
second pair is collapsed into 17 (8 + 9), the third pair is collapsed into
17 (4 + 13) and so on.
If the list stores an odd number of elements, the final element is not
collapsed. For example, if the list had been:
[1, 2, 3, 4, 5]
Then the call on collapse would produce the following list:
[3, 7, 5]
with the 5 at the end of the list unchanged. The method should not
construct any extra data structures other than the array to be returned and
it should not alter its parameter.
10. Programming, 10 points. Write a static method called acronym that takes as
a parameter a string containing a phrase and that returns an acronym for
the phrase. For example, the following call:
acronym("self-contained underwater breathing apparatus")
should return "SCUBA". The acronym is formed by combining the capitalized
first letters of each word in the phrase. Words in the phrase will be
separated by some combination of dashes and spaces. There might be extra
spaces or dashes at the beginning or end of the phrase. The String will
not contain any characters other than dashes, spaces, and letters, and is
guaranteed to contain at least one word. Below are several sample calls.
Method Call Value Returned
----------------------------------------------- --------------
acronym(" automatic teller machine ") "ATM"
acronym("personal identification number") "PIN"
acronym("computer science") "CS"
acronym("merry-go-round") "MGR"
acronym("All my Children") "AMC"
acronym("Troubled Assets Relief Program") "TARP"
acronym("--quite-- confusing - punctuation-") "QCP"
acronym(" loner ") "L"
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.
CSE142 Final Cheat Sheet
Math Method Description ArrayList Types
-------------------------------------- -----------------
Math.abs(n) absolute value of n ArrayList<String>
Math.max(x, y) maximum of x and y ArrayList<Integer>
Math.min(x, y) minimum of x and y
Array Construction: int[] data = new int[size];
String Method Description
-----------------------------------------------------------------------------
charAt(index) character at a specific index
endsWith(text) whether or not string ends with text
equals(text) whether or not string equals text
equalsIgnoreCase(text) whether or not string equals text ignoring case
indexOf(text) index of a particular string (-1 if not found)
length() number of characters in string
startsWith(text) whether or not string starts with text
substring(start, stop) characters from start (inclusive) to stop (exclusive)
substring(start) characters from start to end of string
toLowerCase() a new String with lowercase version of original
toUpperCase() a new String with uppercase version of original
ArrayList method Description
-------------------------------------------------------------------------------
add(value) appends value at end of list
add(index, value) inserts value at index, shifting subsequent values right
clear() removes all elements of the list
contains(value) whether the list contains the value
get(index) returns the value at given index
isEmpty() whether list is empty
remove(index) removes value at index, shifting subsequent values left
set(index, value) replaces value at given index with given value
size() returns the number of elements in list
Critter Details
---------------
getMove returns one of Action.HOP, Action.LEFT, Action.RIGHT, Action.INFECT.
There are methods for finding out what kind of critters are around a critter
(one of Neighbor.WALL, Neighbor.EMPTY, Neighbor.SAME, Neighbor.OTHER):
getFront(), getBack(), getLeft(), getRight()
There is a method getDirection() to find out what direction a critter is facing
(one of Direction.NORTH, Direction.SOUTH, Direction.EAST, Direction.WEST)
public class FlyTrap extends Critter {
public String toString() {
return "T";
}
public Action getMove(CritterInfo info) {
if (info.getFront() == Neighbor.OTHER) {
return Action.INFECT;
} else {
return Action.LEFT;
}
}
public Color getColor() {
return Color.RED;
}
}
]]>
Stuart Reges
Last modified: Fri Sep 16 16:16:07 PDT 2011