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CS 240 Exam 2
Computer Science II
Spring 2003 2/28/03
Page 1
Name _____________________________
1. Mark an ‘X’ in each box that matches the trait to the data structure
[10 pts]
Data
Structure
Array
Record
Stack
Set
Queue
Homogeneous
elements
Linear
organization
Sequential
access
2. Rank the algorithm complexities from "fastest" to "slowest" (increasing dominance). 1 is fastest (good, low cost)
and 6 is slowest (bad, high cost).
[5 pts]
linear
exponential
quadratic
O(log n)
constant
O(n log n)
3. Estimate the running times using the big-O notation for each of these code segments. The size of the data set is n.
[8 pts]
____________
____________
____________
____________
for (i=1; i<=n; i++)
for(j=i; j<=n; j++)
for(k=9; k<=n; k++){
// 4 assignment and 2 i/o statements
}
i = n;
while(i>0){
for(j=i; j<=n; j++){
// 3 assignments
}
if(i % 2 == 1){ // if i is odd
// 2 assignment and 4 i/o statements
}
i = i-3;
}
j=n;
while(j>0){
// 3 assignments
j = j/2;
}
for (k=n; k>0; k--)
j=0;
while (j<n){
foo(j,n); //foo executes in quadratic time
j++;
}
}
CS 240 Exam 2
Page 2
4. Convert the following infix expression to postfix.
[4 pts]
a + b * (c – d) + e
__________________________
5. Evaluate the following postfix expression and prefix expression.
[4 pts]
11 4 + 9 4 2 * + - = __________
+ * - 4 1 5 / 12 4 = __________
6. Memory management.
[6 pts]
a. In the memory layout scheme, where are the activation records stored? ______________________
b. The register that tracks which bytecode is to be executed next is called the ___________ ___________
c. Where are local variables (int, float, char) stored? ________________________________
d. Where is the return address stored during a method call? __________________________________
e. The area or data structure where objects are stored is called a ________________
f.
The process of recovering memory from unreferenced objects is called _______________ ___________
7. Give brief pre- and post-conditions as requested for each of the following queue operations.
[10 pts]
int size();
//post:
void enqueue(Object element);
//pre:
//post:
boolean isEmpty();
//post:
Object dequeue();
//post:
7. Below is an int array. The top row values are the indexes of the elements.
[6 pts]
0
2
1
5
2
8
3
10
4
11
5
16
6
19
7
20
8
22
9
23
10
25
11
28
12
30
13
33
a) What is the basic requirement of the data in order for a binary search to be applicable?
b) List the sequence of probe indexes that would be computed in a binary search when looking for 16.
c) What happens to the internal boundary indexes when a value is not found in a binary search?
14
34
CS 240 Exam 2
Page 3
8. Fill in the blanks below to complete a binary search function on a “full” integer array.
[9 pts]
public static int Lookup(int vec[],int key)
{
int lo = 0 ;
int hi = _____________ ;
while (lo ____ hi){
mid = (lo+hi)________;
if(vec [_____] == _____)
return _____ ;
if (key __ vec [_____]){
lo = mid ________ ;
} else {
hi = mid ________ ;
}
}
___________ -1;
}
9. Fill in the program segment to take a list of positive integers and print them out in reverse order using a stack.
Assume the usual stack operations.
[7 pts]
ArrayStack stack = new ______________ ;
int number = getNumber();
while(str.length() > 0){
stack.____________(( _________ )number);
number = getNumber();
}
while( ! stack.____________){
number = ( _____ ) stack.____________();
System.out.println(____________);
}
10. Below are the methods for push and pop in an array implementation. Fill in the code to complete the
implementation.
[9 pts]
public Object pop(){
if ( _______________ )
throw new StackUnderflowException ("Stack is empty—cannot pop");
__________ topItem = stack[top];
stack[_____] = _______;
top_____;
return ___________;
}
public void push(Object item){
if (item == null)
throw new IllegalArgumentException ("Item is null—cannot push");
if (____________ )
throw new StackOverflowException ("Stack is full—cannot push");
top ____;
stack[_______] = _________;
}
CS 240 Exam 2
Page 4
11. For each of the cost functions below give the “best” big-O equivalence.
[8 pts]
_______ f(n) = 3n2 + 900n + 50
_______ f(n) = 17 + log2n + 5n
_______ f(n) = 10n5 +2n
_______ f(n) = 2n2 + 5k7
12. For each of the data structure operations below, give the algorithm complexity running time cost. Choose from
“constant”, “linear”, “exponential”, and “logarithmic”
[7 pts]
a) ________________ searching an unsorted list for the maximum value
b) ________________ searching a list with a binary search
c) ________________ adding an element to the end of an array (that still has room)
d) ________________ deep copying an array over another array
e) ________________ inserting an element to the middle of an array
f) ________________ pushing an element onto a stack
g) ________________ dequeueing from a circular queue
13. True/False
[7 pts]
______ In the Model-View-Controller design of a GUI application, the controller manages the data.
______ In the MVC design, the view contains the placement of widgets and their interaction.
______ The record data structure is captured in Java’s class facility.
______ An abstract class must be extended to a concrete class for use.
______ An interface provides a set of abstract methods that can be implemented in one or more classes.
______ In event driven programming, a Java event handler is designated for one specific widget.
______ An action listener must be registered or connected with a widget before its events can be recognized.
14. [Extra credit] Consider the purpose of defining the Listable interface. Recall this interface was used in the
RealEstate project and is actually a simplified version of the Java standard Comparable interface. Both
interfaces define an abstract method compareTo. Why abstract out this particular method?
[5 extra credit pts]