CSC212 Midterm Exam Prep 2014

--D. Thiebaut (talk) 17:52, 7 October 2014 (EDT)

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This is a sample of problems to get you ready for the midterm exam. The midterm will be closed-book, closed-computers, and on paper. You can see the answers to the questions by highlighting the white areas under each question.

Problem #1

• Fill in the spaces marked with ____ to complete the following Boolean expressions. Do not use the Boolean operator "!" in your answer. Write only in the spaces marked with ____.

• Assume that X, Y and Z are integer variables.

Question 1

Write the expression that is true if X is strictly the largest of the three variables X, Y and Z. For example, if X is 50, Y is 40 and Z is 45, the expression should be true, but if X is 50, Y is 40, and Z is 50, the expression should be false, since X is not strictly greater than Z.

    (______) _____ (______)

(X > Y) && (X > Z)

Problem #2

• Assume that we have an array of ints, table, declared as follows:

      int[] table = new int[] { 10, 20, 5, 15, 25, 0, 3 };

Question 1

Write the java code required to print all the elements of the array table.

for ( int i=0; i<table.length; i++ )   System.out.println( table[i] );

Question 2

write the java code required to find the largest element of table and print it on the screen.

int max=table[0];
for ( int i=1; i<table.length; i++ )
  if (table[i]>max)
    max = table[i];
System.out.println( table[i] );

Question 3

write the java code required to replace all the 0 element of table with -1.

for ( int i=1; i<table.length; i++ )
  if (table[i]==0) table[i] = -1;

Problem #3

Given this code, and assuming that the user enters the number 3 at the keyboard, followed by ENTER; what is the output of the program?

                Scanner scan = new Scanner( System.in );
		int n, k, max;
		max = scan.nextInt(); /* read value for max */
		for (n = 0; n < max; n++) {
			for (k = 0; k < max; k++) {
				if (n > k)
					System.out.print(" G ");
				else if (n < k)
					System.out.print(" L ");
				else
					System.out.print(" E ");
			}
			System.out.println();
		}

3
E L L
G E L
G G E

Problem #4

• Assume the ArrayList fibonacci is initialized as follows:

ArrayList fibonacci = new ArrayList();

fibonacci.add( 1 );
fibonacci.add( 1 );

Question 1

Write a for-loop that will compute 10 more fibonacci term and store them in the array.

for (int i=2; i<2+10; i++)
  fibonacci.add( (int) fibonacci.get( i-1 ) + (int) fibonacci.get( i-2 ) );

Question 2

Same question, but using a LinkedList instead of an ArrayList.

LinkedList fibonacci = new LinkedList();
for (int i=2; i<2+10; i++)
  fibonacci.add( (int) fibonacci.get( i-1 ) + (int) fibonacci.get( i-2 ) );

ArrayList

use add( Object o ) to add an element, and get( int index) to access an element at some location.

LinkedList

use add( Object o ) to add an element, and get( int index ) to access an element at some location.

Problem #5

Question 1

In a singly-linked list containing several thousands of items, do the remove-from-tail and the remove-from-front operations take the same amount of time to operate? Why or why not?

No, the remove from tail requires a loop to find the node that points to the last node in the list, so that the pointer tail can be moved to that one-before-last node. So the remove-from-tail requires looping thousands of time to get to the one-before-last node. Remove-from-front requires only a fixed number of operations.

Problem #6

Question 1

Write the code necessary to remove the node containing the string "beta" from the list. The result should be a list containing the series "alpha", "delta", and "epsilon".

IntDLLNode temp = head.next;
head.next = temp.next;
temp.next.prev = head;

Question 2

Write the code that will print the contents of all the cells of a doubly-linked list, no matter how many nodes it contains.

IntDLLNode temp = head;
while ( temp != null ) {
  System.out.println( temp.info );
  temp = temp.next;
}

Problem #7

Question 1

What is a circular list?

See Section 3.3 in Drozdek

Question 2

What is a skip-list? What is its advantage?

See Section 3.4 in Drozdek