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CSE142 Sample Final, Spring 2016 handout #19
1. Reference Mystery, 5 points. What output is produced by this program?
import java.util.*;
public class ReferenceMystery {
public static void main(String[] args) {
int x = 4;
int y = 8;
int[] data = {5, 10, 15};
x = mystery1(y, data);
System.out.println(y + " " + Arrays.toString(data));
mystery2(x, y);
System.out.println(x + " " + y);
}
public static int mystery1(int n, int[] numbers) {
n = n + 100;
numbers[2]--;
System.out.println(n + " " + Arrays.toString(numbers));
return numbers[1] * 2;
}
public static void mystery2(int x, int y) {
x++;
y = y * 3;
}
}
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 - 1; i++) {
if (list[i] <= list[i + 1]) {
list[i + 1] = 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
-----------------------------------------------------------------
{4, 1, 3} _________________________________
{2, 1, 3, 2} _________________________________
{3, 6, 2, 9, 5} _________________________________
{1, 1, 1, 1, 8} _________________________________
{1, 3, 4, 6, 2, 9} _________________________________
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
reportScore that takes as a parameter a Scanner containing information about
a student's performance and that prints a report for that student. Students
are given gold stars for tasks they solved particularly well and minuses for
tasks where they performed poorly. The information for each student is
presented as a series of count/type pairs where each count is a positive
integer and each type is either "*" or "-". These count/type pairs are
followed by the student's name which is guaranteed to be a single word
composed entirely of alphabetic characters. Consider this report:
3 * 2 - 1 * Erica
It indicates that Erica got 3 stars followed by 2 minuses followed by 1
star. The overall score is computed by giving 1 plus point for each star
and one minus point for each minus. The method produces exactly one line of
output reporting this score and the total number of tasks. The table below
includes several examples.
Scanner contents Output produced
---------------------------------- ------------------
3 * 2 - 1 * Erica Erica got 2 of 6
2 - 1 * 2 - 1 - 1 * 2 - Fred Fred got -5 of 9
1 * 1 - 3 * 1 - 2 - Sylvia Sylvia got 0 of 8
Julia Julia got 0 of 0
You may not construct any extra data structures to solve this problem.
5. Line-Based File Processing, 9 points. Write a static method called
reverseAndFlip 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 and with the second line of each pair reversed. 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 method switches the order of the first two lines, printing the second
line reversed. Then it switches the order of the third and fourth lines,
print the fourth line reversed. And so on. It should produce this output:
.ebaw eht ni elbmig dna eryg did
Twas brillig and the slithy toves
.ebargtuo shtar emom eht dna
All mimsey were the borogroves,
,nos ym ,kcowrebbaJ eht eraweB"
nuhs dna drib buJbuJ eht eraweB
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 and you may not
construct any extra data structures to solve this problem.
6. Arrays, 10 points. Write a static method called isPairwiseSorted that takes
an array of integers as a parameter and that returns whether or not the
array is pairwise sorted. An array is considered to be pairwise sorted if
it contains a sequence of pairs where each pair is in sorted (nondecreasing)
order. For example, if a variable list is defined as follows:
int[] list = {3, 8, 2, 15, -3, 5, 2, 3, 4, 4};
then the call isPairwiseSorted(list) would return true because the array is
composed of a sequence of pairs that are each in sorted order ((3, 8)
followed by (2, 15), followed by (-3, 5), and so on). If the array has an
odd length, then your method should ignore the value at the end. Below are
several examples of what value would be returned for a given array.
Array passed as parameter Value Returned
-------------------------------------- --------------
{} true
{6} true
{4, 12} true
{8, 5} false
{3, 8, 2, 15, -3, 5, 2, 3, 4, 4, 3, 1} false
{8, 13, 92, 92, 4, 4} true
{1, 3, 5, 7, 9, 8} false
You may not construct any extra data structures to solve this problem.
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. See the cheat sheet for a list
of available ArrayList methods.
8. Critters, 15 points. Write a class called Ferret that extends the Critter
class. The instances of the Ferret class always infect when an enemy is in
front of them, otherwise hop if possible, and otherwise randomly choose
between turning left and turning right (each choice equally likely). Their
appearance changes based on whether they recently attempted to infect. They
initially display as "I=0" indicating that they have not attempted to infect
recently. After an infect move, they should display as "I=5". As the
ferret makes other moves that are not infecting, this display should change
to "I=4", "I=3", "I=2", "I=1", and "I=0". It should then stay at "I=0".
Notice, however, that it can go back to "I=5" in the middle of this process
because it might infect again before reaching "I=0". The ferrets should be
blue when they are displaying as "I=0" and red otherwise.
Use a Random object to make random choices but each Ferret should construct
only one such object. As in assignment 8, fields must be declared private,
fields initialized to a non-default value must be set in a constructor, and
all updates to fields must occur in the getMove method.
9. Arrays, 15 points. Write a static method called splice that takes
as parameters an array of integers and a "from index" (inclusive) and "to
index" (exclusive) and that returns a new array containing the result of
splicing together three segments of the array. The from and to indexes
specify a sublist. For example, if list stores the following:
[7, 5, 8, 5, 9, 7, 2, 3]
then the call splice(list, 2, 4) indicates that the array should be
rearranged using the sublist from 2 to 4:
[7, 5] [8, 5] [9, 7, 2, 3]
before sublist sublist after sublist
The new array should contain the values after the sublist followed by the
values in the sublist followed by the values before the sublist. For this
example, it would return [9, 7, 2, 3, 8, 5, 7, 5].
You may assume that the indexes passed as parameters specify a legal sublist
of the list, although it might be empty. The method should not construct
any extra data structures other than the array to be returned and it should
not alter its array parameter. You are not allowed to call methods of the
Arrays class to solve this problem.
10. Programming, 10 points. Write a static method called isMatch that takes a
pattern string and a target string as parameters and that returns whether
or not the given target matches the pattern. Patterns can contain special
wildcard characters dot (".") and star ("*"). If a pattern does not
contain any wildcards, then the target has to be the same string, as in
isMatch("and", "and"). A dot can match any single character. For example,
the pattern "a.." matches any 3-letter string beginning with the letter
"a". A star can match any sequence of characters (including no
characters). For example, the pattern "a*t" matches any string that begins
with "a" and ends with "t", including "at". There will be at most one star
in any given pattern, although a pattern can contain several dots and a
star. Below are examples of patterns and matching strings (note that your
method compares a pattern against a single string, not a list of strings).
Pattern Matching strings
--------- -----------------------------------------------------
"hello" hello
"..." and, ant, but, cat, cow, hat, sat, tap, ten, the, tot
"a..." atom, army, aunt, aura
".a.." bats, task, yard, saga, lava
"...a" tuna, soda, coma, aura, saga, lava
"....th" growth, zenith, health
"a*" a, an, at, and, ant, atom, aunt, apple, army, aura
"t*t" tot, that, trot, tiniest
"the*" the, then, there, therefore, thermal, thespians
".a*a" saga, lava, saliva, tarantula, nausea
"t.e.p*" twerp, trespass, thespians
".o*e." poem, token, wolves, voucher, toothbrushes
You are allowed to create new strings, but otherwise you are not allowed to
construct extra data structures to solve this problem (no array, ArrayList,
Scanner, etc). You are limited to the string methods listed on the cheat
sheet (otherwise this problem can be solved in one line of code).
You can receive up to 6 points for a solution that handles the dot wildcard
without handling the star wildcard. If you wish to pursue this option,
please mark the box below:
+---+
| | I agree to limit my score to 6 by handling just the dot wildcard
+---+
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