C, input from file to 2d array

Question

Can any one explain to me how to make a C program to read input from a file according to the following scenario:

12
2-4,7,9;
1,4,11-12;
1,4,10,12;
1,4-8,10-12;
1,8;
1,3-6,8,10-12;
1,3,5-6,8,11;
1,8,10-12;
1-8;
;
2;
2-4,7-10,12;

The first number (on the first line) describes what size the grid should be, in this case a 12x12 grid. The following lines describe how many cells are occupied on each row of the grid. For example, in the first row the cells from 2 to 4 and 7 and 9 are occupied; in the second row, the cells 1, 4 and from 11 to 12 are occupied and so on.

Right now I have this code, but it is not solving my problem ...

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

void main()
{   
    char content[3000];

    int value;
    FILE *ptr_file = fopen("data.txt", "r");
    if(!ptr_file)
        return 1;
    int j;

    while(fgets(content, 3000, ptr_file)!=NULL){
        printf("%s", content);
        value = atoi(content);   

        for(j=0; j<3000; j++){
            value = content[j];
            printf("%i", value);
        }
    }
    return 0;
}

Console throws just a bunch of random numbers ...

Answer 1

Pseudo-code:

Open your file
Read the first line
    Extract the value N
    Allocate your grid
Loop N times
    Read a line
    If not an empty line, ie. semi-colon only
       Split into tokens by comma
       Check for a range or a single digit
       Extract numbers
       Set cells accordingly

Answer 2

The "random" numbers are the byte values from your file and you forgot to stop at end of line. Dave's solution is not quite right for c. After read a line:

while not semicolon
    strtoul a number
    if no number
        exit error
    if next char is hyphen
        shift to next char
        strtoul end of range
        if no number
            exit error
        set cells
    else
        set cell
    if next char is not semicolon
        shift to next char

You should not use atoi for anything ever. Use sscanf or strto….

Answer 3

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

enum { EOD = -1, EOL = -2, ERR = -3, OFF = 0, ON = 1 };//End Of Data, End Of Line

int getValue(FILE *fp){
    static int on_yield = OFF, prev, end;

    if(on_yield == ON && prev < end){
        return ++prev;
    }
    on_yield = OFF;

    int n, ch = fgetc(fp);

    if(ch == EOF)
        return EOD;
    else if(ch == ';')
        return EOL;
    else if(ch == ',' || ch == '\n')
        return getValue(fp);//or change to using loop
    else if(isdigit(ch)){
        ungetc(ch, fp);
        fscanf(fp, "%d", &n);
        return prev=n;
    } else if(ch == '-'){
        on_yield = ON;
        fscanf(fp, "%d", &n);
        end = n;
        return getValue(fp);
    }
    fprintf(stderr, "(%c) invalid format in file\n", ch);
    return ERR;
}

int main(void){
    FILE *ptr_file = fopen("data.txt", "r");
    if(!ptr_file){
        perror("fopen");
        return 1;
    }

    int size;
    fscanf(ptr_file, "%d", &size);//check omitted
    char (*cell)[size] = malloc(size * sizeof(*cell));
    memset(&cell[0][0], ' ', size*size);

    int r = 0, c, value;
    while((value=getValue(ptr_file))!=EOD){
        if(value == EOL){
            ++r;
            continue;
        }
        if(value > 0)
            cell[r][value-1] = '*';
    }
    fclose(ptr_file);

    for(r = 0; r < size; ++r){
        for(c = 0; c < size; ++c){
            putchar(cell[r][c]);
        }
        putchar('\n');
    }
    free(cell);

    return 0;
}