CODEWITHSUNDEEP
carraysindexing
Hunter
Hunter

Reputation: 29

Handling arrays in C

I'm just a beginner with C language.

I want to determine elements of array, but it failed. I'd like to insert index(row=x, column=y). Is this possible?

Here's my code.

#include <stdio.h>
#define _CRT_SECURE_NO_WARNINGS

int main(void)
{
    int x, y;
    char coords[3][3] = { NULL };

    printf("x, y: ");
    scanf("%d %d", &x, &y);


    coords[x][y] = 'O';




    for (int i = 0; i < 3; i++)
    {
        for (int j = 0; j < 3; j++)
            printf("%c ", coords[i][j]);
        printf("\n");
    }

    return 0;
}

If x=2, y=2, I expect the outcome to be printed 

␠␠␠
␠␠␠
␠␠O

(Where ␠ is a space)

I think coords[x][y] = 'O'; is the problem, but i can't fix it.

Upvotes: 1

Views: 85

Answers (2)

KamilCuk
KamilCuk

Reputation: 142025

First:

char coords[3][3] = { NULL };

The NULL makes little sense in here, although the compiler will most probably compile the code and initialize all elements to zero. Let's fix it to something more "correct":

char coords[3][3] = { { 0 } };

The array elements not initialized explicitly are initialized to 0. For a reference, you could read array initialization on cppreference.

Now we know that all out array elements are initialized with 0. So you can check them before printing:

for (int i = 0; i < 3; i++) {
    for (int j = 0; j < 3; j++) {
        if (coords[i][j] == 0) {
            printf(" ");
        } else {
            printf("%c", coords[i][j]);
        }
        printf(" ");
    }
    printf("\n");
}

Alternatively, you could initialize all array elements to ' ' character as suggested in the other answer.

Upvotes: 2

Adrian Mole
Adrian Mole

Reputation: 51905

You have not initialized your coords array as you perhaps think! The line:

char coords[3][3] = { NULL };

actually gives all 9 elements the value of zero - which is the nul (unprintable) character. (If there are less initializers in the list than array elements, all 'extra' elements will be given the value of zero.)

What you perhaps want (to set all 9 elements to the blank space) is:

char coords[3][3] = { {' ', ' ', ' '}, {' ', ' ', ' '}, {' ', ' ', ' '} };

Or something similar, like using the ASCII value for the space (32) if you know your system uses ASCII encoding (which it is not obliged to).

Better would be to define your desired initial value as a constant, then use that as the initializer:

const char X = ' ';
char coords[3][3] = { {X, X, X}, {X, X, X}, {X, X, X} };

as this makes it easier to change things (less typing) if you need to use a different initial character.

Upvotes: 3

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