GATE CS 2022 Q.43: Pointers, Arrays and Strings

What is printed by the following ANSI C program?

#include<stdio.h>
int main(int argc, char *argv[])
{
       int a[3][3][3] =
       {{1, 2, 3, 4, 5, 6, 7, 8, 9},
        {10, 11, 12, 13, 14, 15, 16, 17, 18},
        {19, 20, 21, 22, 23, 24, 25, 26, 27}};
        int i = 0, j = 0, k = 0;
        for( i = 0; i < 3; i++ ){
               for(k = 0; k < 3; k++ )
                     printf("%d ", a[i][j][k]);
               printf("\n");
        }
        return 0;
}

1 2 3
10 11 12
19 20 21

1 4 7
10 13 16
19 22 25

1 2 3
4 5 6
7 8 9

1 2 3
13 14 15
25 26 27

Official answer and solution

Official answer: A
From: Official GATE 2022 answer key

Solution

Trace the array indices accessed in the nested loops.

The array $a[3][3][3]$ is initialized with 27 elements:

Slice $i=0$ : rows of 3 elements: $\{1, 2, 3\}, \{4, 5, 6\}, \{7, 8, 9\}$
Slice $i=1$ : rows of 3 elements: $\{10, 11, 12\}, \{13, 14, 15\}, \{16, 17, 18\}$
Slice $i=2$ : rows of 3 elements: $\{19, 20, 21\}, \{22, 23, 24\}, \{25, 26, 27\}$

The loop variables are $i$ (outer loop from 0 to 2) and $k$ (inner loop from 0 to 2), while $j$ remains fixed at $0$ :

Outer loop $i = 0$ : prints $a[0][0][0], a[0][0][1], a[0][0][2] \implies 1\ 2\ 3$
Outer loop $i = 1$ : prints $a[1][0][0], a[1][0][1], a[1][0][2] \implies 10\ 11\ 12$
Outer loop $i = 2$ : prints $a[2][0][0], a[2][0][1], a[2][0][2] \implies 19\ 20\ 21$

Each iteration of the outer loop concludes with a newline, printing:

1 2 3
10 11 12
19 20 21

This matches Option (A).

Final answer

Option (A)

Common trap

Assuming $j$ increments with $i$ or $k$ , whereas $j$ is constant at 0 throughout.

The answer is the one in the official GATE answer key. The solution is this site's own explanation.

Source

Paper: GATE 2022 Computer Science and Information Technology (CS)
Question: 43 of 65
Section: Computer Science and Information Technology

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