GATE Overflow Test Series | Programming | Test 1 | Question: 17

Question

Consider the following C program fragment:

#include<stdio.h>
int my_array[20][10];
int main()
{
    int *p = my_array, i;
    for(i = 0; i < 10*20; i++)
    {
       *(p+X) = i;
    }
    ...
}

The correct replacement for 'X' so that every position in the array my_array gets initialized is

• A. (i / 20) * 10 + (i% 20) * 10;
• B. (i % 20) * 10 + (i / 20) * 10;
• C. (i / 10) * 20 + (i% 10) * 20;
• D. (i % 10) + (i / 10) * 10;

Answer 1

This is linearization of a $2$-D array.

$i/10$ gives the row number in $2$D and $i\%10$ gives the column number.

Correct Option: D.

Comments

No. Because 5/2 = 2 in C, not 2.5.

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In option D, consider the expressions to right and left of ‘+’. Right side expression gives integer part and left part of ‘+’ gives reminder.  That should make this expression equal to i.

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Yes, exactly. I missed that in the earlier comment.

Answer 2

    #include<stdio.h>
    int my_array[2][3];
    int main()
    {
        int *p = my_array, i;
        for(i = 0; i < 2*3; i++)
        {
           *(p+(i % 3) + (i / 3) * 3) = i;
        }
        
    }