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CSE143 Midterm
Winter 2016
Name of Student_______________________________________________________________
Section (e.g., AA)___________________ TA_____________________________________
The exam is divided into six questions with the following points:
# Problem Area Points Score
---------------------------------------------
1 Recursive Tracing 15 _____
2 Recursive Programming 15 _____
3 Details of Inheritance 20 _____
4 Linked Lists 15 _____
5 Stacks/Queues 25 _____
6 Array Programming 10 _____
----------------------------
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 can also request scratch paper from a TA. You are not
allowed to access any of your own papers during the exam.
The exam is not, in general, graded on style and you do not need to include
comments. For the stack/queue question, however, you are expected to use
generics properly and to declare variables using interfaces when possible.
The cheat sheet mentions important restrictions on Stacks and Queues that you
must follow.
You are allowed to abbreviate "compiler error" and "runtime error" for the
inheritance question (as in "ce" and "re" or "c.e." and "r.e."), but you should
otherwise NOT use any abbreviations on the exam.
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. Recursive Tracing, 15 points. Consider the following method:
public void mystery(int x) {
if (x <= 0) {
System.out.print(".");
} else if (x % 2 == 0) {
System.out.print(x % 10);
mystery(x / 10);
} else {
mystery(x / 10);
System.out.print(x % 10);
}
}
For each call below, indicate what output is produced:
Method Call Output Produced
mystery(7); _____________________________________
mystery(246); ______________________________________
mystery(195); ______________________________________
mystery(1234); ______________________________________
mystery(29548); ______________________________________
2. Recursive Programming, 15 points. Write a recursive method called
printPattern that takes an integer n as a parameter and that prints exactly
n characters composed of nested parentheses and square brackets. The nested
parentheses and brackets should alternate with the innermost pair being
parentheses. For example, printPattern(8) should print:
[([()])]
The output does not include a println. If n is odd, the method should print
a period in the center, as in printPattern(9) which prints:
[([(.)])]
Below are more examples of calls and the output produced.
Method Call Output Produced
-------------------------------------
printPattern(1) .
printPattern(2) ()
printPattern(3) (.)
printPattern(4) [()]
printPattern(5) [(.)]
printPattern(6) ([()])
printPattern(7) ([(.)])
The method should produce no output when passed 0 and should throw an
IllegalArgumentException if passed a negative value. You are not allowed to
construct any structured objects to solve this problem (no string, array,
ArrayList, StringBuilder, Scanner, etc) and you may not use a while loop,
for loop or do/while loop to solve this problem; you must use recursion.
3. Details of inheritance, 20 points. Assuming that the following classes have
been defined:
public class Clock extends Bear {
public void method3() {
System.out.println("Clock 3");
}
}
public class Lamp extends Can {
public void method1() {
System.out.println("Lamp 1");
}
public void method3() {
System.out.println("Lamp 3");
}
}
public class Bear extends Can {
public void method1() {
System.out.println("Bear 1");
}
public void method3() {
System.out.println("Bear 3");
super.method3();
}
}
public class Can {
public void method2() {
System.out.println("Can 2");
method3();
}
public void method3() {
System.out.println("Can 3");
}
}
And assuming the following variables have been defined:
Object var1 = new Bear();
Can var2 = new Can();
Can var3 = new Lamp();
Bear var4 = new Clock();
Object var5 = new Can();
Can var6 = new Clock();
In the table below, indicate in the right-hand column the output produced by
the statement in the left-hand column. If the statement produces more than one
line of output, indicate the line breaks with slashes as in "a/b/c" to indicate
three lines of output with "a" followed by "b" followed by "c". If the
statement causes an error, fill in the right-hand column with either the phrase
"compiler error" or "runtime error" to indicate when the error would be
detected.
Statement Output
------------------------------------------------------------
var1.method2(); ____________________________
var2.method2(); ____________________________
var3.method2(); ____________________________
var4.method2(); ____________________________
var5.method2(); ____________________________
var6.method2(); ____________________________
var1.method3(); ____________________________
var2.method3(); ____________________________
var3.method3(); ____________________________
var4.method3(); ____________________________
var5.method3(); ____________________________
var6.method3(); ____________________________
((Lamp)var6).method1(); ____________________________
((Can)var1).method1(); ____________________________
((Can)var1).method2(); ____________________________
((Bear)var1).method3(); ____________________________
((Bear)var6).method1(); ____________________________
((Clock)var1).method1(); ____________________________
((Clock)var4).method2(); ____________________________
((Bear)var3).method1(); ____________________________
4. Linked Lists, 15 points. Fill in the "code" column in the following table
providing a solution that will turn the "before" picture into the "after"
picture by modifying links between the nodes shown. You are not allowed to
change any existing node's data field value and you are not allowed to
construct any new nodes, but you are allowed to declare and use variables of
type ListNode (often called "temp" variables). You are limited to at most
two variables of type ListNode for each of the four subproblems below.
You are writing code for the ListNode class discussed in lecture:
public class ListNode {
public int data; // data stored in this node
public ListNode next; // link to next node in the list
<constructors>
}
As in the lecture examples, all lists are terminated by null and the
variables p and q have the value null when they do not point to anything.
before after code
-----------------------+-----------------------+-------------------------------
| |
p->[1]->[2] | p->[1]->[2]->[3] |
| |
| |
q->[3] | q |
| |
-----------------------+-----------------------+-------------------------------
| |
p->[1]->[2]->[3] | p->[1]->[3] |
| |
| |
q | q->[2] |
| |
-----------------------+-----------------------+-------------------------------
| |
| |
p->[1]->[2] | p->[2]->[3] |
| |
| |
q->[3]->[4] | q->[1]->[4] |
| |
| |
| |
| |
-----------------------+-----------------------+-------------------------------
| |
| |
p->[1]->[2]->[3] | p->[3]->[1] |
| |
| |
q->[4]->[5] | q->[5]->[2]->[4] |
| |
| |
| |
| |
| |
| |
| |
| |
| |
-----------------------+-----------------------+-------------------------------
5. Stacks/Queues, 25 points. Write a method called mirror that takes a stack
of integers as a parameter and that doubles the size of the stack by
appending the mirror image of the original sequence at the top of the stack.
The mirror image is the same sequence of values in reverse order. For
example, suppose that a variable called s stores the following values:
bottom [1, 3, 2, 7] top
and we make the following call:
mirror(s);
then it should store the following values after the call:
bottom [1, 3, 2, 7, 7, 2, 3, 1] top
Notice that it has been doubled in size by having the original sequence
appear in reverse order at the top of the stack. If the original stack is
empty, your method should not change it.
You are to use one queue as auxiliary storage to solve this problem. You
may not use any other auxiliary data structures to solve this problem,
although you can have as many simple variables as you like. You also may
not solve the problem recursively. Your solution must run in O(n) time
where n is the size of the stack. Use the Stack and Queue structures
described in the cheat sheet and obey the restrictions described there
(recall that you can't use the peek method or a foreach loop or iterator).
6. Array Programming, 10 points. Write a method called removeRange that takes
as parameters a "from" index (inclusive) and "to" index (exclusive) and that
removes the values in the given range from a list of integers. For example,
if a variable called list stores the following values:
[8, 13, 17, 4, 9, 12, 98, 41, 7, 23, 0, 92]
and you make the following call:
list.removeRange(3, 8);
values starting at index 3 (the value 4) and up to but not including index 8
(the value 7) are removed:
[8, 13, 17, 4, 9, 12, 98, 41, 7, 23, 0, 92]
| |
+--------------+
to remove
thus, the list should store the following values after the call:
[8, 13, 17, 7, 23, 0, 92]
Your method should throw an IllegalArgumentException if either index is not
legal. Start has to be less than or equal to stop and both have to be
between 0 and the size of the list inclusive. If start equals stop, the
method should not change the list because the specified sublist is empty.
You are writing a method for the ArrayIntList class discussed in lecture:
public class ArrayIntList {
private int[] elementData; // list of integers
private int size; // current # of elements in the list
<methods>
}
You may not call any other methods of the ArrayIntList class to solve this
problem, you are not allowed to define any auxiliary data structures (no
array, String, ArrayList, etc), and your solution must run in O(n) time.
You are not allowed to call System.arraycopy to solve this problem.
CSE143 Midterm Cheat Sheet
Queues should be constructed using the Queue<E> interface and the
LinkedList<E> implementation. For example, to construct a queue of String
values, you would say:
Queue<String> q = new LinkedList<String>();
Stacks should be constructed using the Stack<E> class (there is no interface).
For example, to construct a stack of String values, you would say:
Stack<String> s = new Stack<String>();
To transfer from a queue to a stack:
while (!q.isEmpty()) {
s.push(q.remove());
}
To transfer from a stack to a queue:
while (!s.isEmpty()) {
q.add(s.pop());
}
-------------------------------------------------------------------------------
For Stack<E>, you are limited to the following operations:
public void push(E value); // push given value onto top of the stack
public E pop(); // removes and returns the top of the stack
public boolean isEmpty(); // returns whether or not stack is empty
public int size(); // returns number of elements in the stack
For Queue<E> you are allowed the following operations:
public void add(E value); // inserts given value at the end of the queue
public E remove(); // removes and returns the front of the queue
public boolean isEmpty(); // returns whether or not queue is empty
public int size(); // returns number of elements in the queue
YOU ARE NOT ALLOWED TO USE FOREACH LOOPS OR ITERATORS FOR EITHER STRUCTURE.
-------------------------------------------------------------------------------
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Stuart Reges
Last modified: Fri Sep 16 16:16:07 PDT 2011