GATE-CS-2004

Question 31

Consider the following program fragment for reversing the digits in a given integer to obtain a new integer. Let n = D1D2…Dm

C

int n, rev;
rev = 0;
while (n > 0)
{
   rev = rev*10 + n%10;
   n = n/10;
}

The loop invariant condition at the end of the ith iteration is:

• n = D1D2….Dm-i and rev = DmDm-1…Dm-i+1
• n = Dm-i+1…Dm-1Dm and rev = Dm-1….D2D1
• n != rev
• n = D1D2….Dm and rev = DmDm-1…D2D1

Question 32

Consider the following C program segment:

C

char p[20];
char *s = \"string\";
int length = strlen(s);
int i;
for (i = 0; i < length; i++)
     p[i] = s[length — i];
printf(\"%s\",p);

The output of the program is (GATE CS 2004)

• gnirts

• gnirt

• string

• no output is printed

Question 33

Which of the following language supports polymorphism but not the classes?

• Java

• C++

• Ada

• C#

Question 34

Consider the label sequences obtained by the following pairs of traversals on a labeled binary tree. Which of these pairs identify a tree uniquely ?

(i)     preorder and postorder
(ii)    inorder and postorder
(iii)   preorder and inorder
(iv)   level order and postorder

• (i) only
• (ii), (iii)
• (iii) only
• (iv) only

Question 35

A circularly linked list is used to represent a Queue. A single variable p is used to access the Queue. To which node should p point such that both the operations enQueue and deQueue can be performed in constant time?

• rear node
• front node
• not possible with a single pointer
• node next to front

Question 36

The elements 32, 15, 20, 30, 12, 25, 16 are inserted one by one in the given order into a Max Heap. The resultant Max Heap is.

• a
• b
• c
• d

Question 37

Assume that the operators +, -, × are left associative and ^ is right associative. The order of precedence (from highest to lowest) is ^, x , +, -. The postfix expression corresponding to the infix expression a + b × c - d ^ e ^ f is

• abc × + def ^ ^ -

• abc × + de ^ f ^ -

• ab + c × d - e ^ f ^

• - + a × bc ^ ^ def

Question 38

Two matrices M1 and M2 are to be stored in arrays A and B respectively. Each array can be stored either in row-major or column-major order in contiguous memory locations. The time complexity of an algorithm to compute M1 × M2 will be

• best if A is in row-major, and B is in column- major order
• best if both are in row-major order
• best if both are in column-major order
• independent of the storage scheme

Question 39

Suppose each set is represented as a linked list with elements in arbitrary order. Which of the operations among union, intersection, membership, cardinality will be the slowest?

• union only

• intersection, membership

• membership, cardinality

• union, intersection

Question 40

Consider the following C program

C

main()
{
    int x, y, m, n;
    scanf (\"%d %d\", &x, &y);
    /* Assume x > 0 and y > 0  */
    m = x;
    n = y;
    while (m! = n)
    {
        if (m > n)
            m = m - n;
        else
            n = n - m;
    }
    print f (\"% d\", n);
}

The program computes

• x ÷ y using repeated subtraction
• x mod y using repeated subtraction
• the greatest common divisor of x and y
• the least common multiple of x and y