C Language | Set 7

Following questions have been asked in GATE CS 2010 exam. 1. What does the following program print? C

#include<stdio.h>
void f(int *p, int *q)
{
  p = q;
 *p = 2;
}
int i = 0, j = 1;
int main()
{
  f(&i, &j);
  printf("%d %d \n", i, j);
  getchar();
  return 0;
}

(A) 2 2 (B) 2 1 (C) 0 1 (D) 0 2 Answer (D) See below f() with comments for explanation. C

/* p points to i and q points to j */
void f(int *p, int *q)
{
  p = q;    /* p also points to j now */
 *p = 2;   /* Value of j is changed to 2 now */
}

2. What is the value printed by the following C program? C

#include<stdio.h>
int f(int *a, int n)
{
  if(n <= 0) return 0;
  else if(*a % 2 == 0) return *a + f(a+1, n-1);
  else return *a - f(a+1, n-1);
}

int main()
{
  int a[] = {12, 7, 13, 4, 11, 6};
  printf("%d", f(a, 6));
  getchar();
  return 0;
}

(A) -9 (B) 5 (C) 15 (D) 19 Answer (C) f() is a recursive function which adds f(a+1, n-1) to *a if *a is even. If *a is odd then f() subtracts f(a+1, n-1) from *a. See below recursion tree for execution of f(a, 6). .

 f(add(12), 6) /*Since 12 is first element. a contains address of 12 */
    |
    |
 12 + f(add(7), 5) /* Since 7 is the next element, a+1 contains address of 7 */
        |
        |
     7 - f(add(13), 4)
              |
              |
           13 - f(add(4), 3)
                     |
                     |
                  4 + f(add(11), 2)
                             |
                             |
                           11 - f(add(6), 1)
                                    |
                                    |
                                 6 + 0

So, the final returned value is 12 + (7 - (13 - (4 + (11 - (6 + 0))))) = 15 Please see GATE Corner for all previous year paper/solutions/explanations, syllabus, important dates, notes, etc. Please write comments if you find any of the answers/explanations incorrect, or you want to share more information about the topics discussed above.