fscanf into a 2d array in C

Question

I want to scan elements from a txt into an array. The txt doesn't have how many rows or columns I'm going to have, it only contains a coordinate, and the elements of the array. It looks like this:

2,3
2,1
3,0
-

How can i put these numbers into an array so that array[0][0] will be 2 and array[1][0] will be 3 etc...

I want to make this work with other inputs as well.

My code so far :

The ?? is there because I have no idea how I should declare these if I don't even know how many rows or columns every input txt will have.

#include <stdio.h>
#include <stdlib.h>

int main()
{
FILE* in = fopen("in.txt", "r");

int x, y;

int array[??][??];

if (in == NULL) {
    printf("Can't open in.txt");
    fclose(in);
    return 1;
}

if (fscanf(in, "%d,%d\n", &x, &y) != 2) {
    printf("Cant read file.");
    return 2;
}

for (int i = 0; i < ??; i++) {
    for (int j = 0; j < ??; j++)
    fscanf(in, "%d", &array[i][j]);
}

return 0;
}

Answer 1

You want to read in a list of value pairs? That sounds like you will need to have a (possibly long) array of sets of two numbers. Rather than remembering that X is the first and Y is the second, may I suggest setting up a structure to hold the values. Something like this should work:

int main()
{
    FILE* in = fopen("lis.csv", "r");
    int count=0;
    int error=0;
    int x, y;
    typedef struct {
        int x;
        int y;
    } COORD;
    COORD array[999]={0};
    if (in == NULL) {
        printf("Can't open in.txt");
        fclose(in);
        return 1;
    }
    while(!feof(in))
    {
        if (fscanf(in, "%d,%d\n", &x, &y) != 2) {
            printf("Cant read file.");
            error=1;
            break;
        }
        array[count].x=x;
        array[count].y=y;
        count++;
    }
    return error;
}

I did not add anything bright for the error condition and it helps if you do something with the values after reading them in but you get the idea.

Answer 2

You should use dynamic array allocation to scan elements from an unknown txt file into an array. for C++ programmers the best solution is std::vector. but C programmers should use alternative solutions. please read this post: (std::vector alternative for C)