Which one of the choices given below would be printed when the following…
2006
Which one of the choices given below would be printed when the following program is executed?
#include
void swap (int *x, int *y)
{
static int *temp;
temp = x;
x = y;
y = temp;
}
void printab ()
{
static int i, a = -3, b = -6;
i = 0;
while (i <= 4)
{
if ((i++)%2 == 1) continue;
a = a + i;
b = b + i;
}
swap (&a, &b);
printf("a = %d, b = %d\\n", a, b);
}
main()
{
printab();
printab();
}
- A.
a = 0, b = 3
a = 0, b = 3 - B.
a = 3, b = 0
a = 12, b = 9 - C.
a = 3, b = 6
a = 3, b = 6 - D.
a = 6, b = 3
a = 15, b = 12
Attempted by 121 students.
Show answer & explanation
Correct answer: D
Explanation: a and b are static and initialized once to -3 and -6. They retain their values across calls to printab.
Key detail about the loop:
The condition uses (i++)%2, so the test uses the old i and then i is incremented. When the test is false, the code uses the incremented i for the additions.
For i starting at 0 the additions performed are when i becomes 1, 3, and 5 (i.e., values 1, 3, 5). Their sum is 9.
Compute values after the first call:
a = -3 + (1 + 3 + 5) = -3 + 9 = 6
b = -6 + (1 + 3 + 5) = -6 + 9 = 3
About the swap function:
The function assigns the pointer parameters to each other (and uses a static pointer), but it does not dereference the pointers to swap the pointed-to values. Therefore a and b remain unchanged by the call.
Second call:
a increases by another 9: 6 + 9 = 15
b increases by another 9: 3 + 9 = 12
Final output:
a = 6, b = 3
a = 15, b = 12