Create a dynamic array and initialize it

Question

for a school project, we have to create a maze in c, I'm a beginner in that language, so I'm stuck at the very beginning: creating an array dynamically...

I read about malloc and calloc, and tried to use it but with no success...

here is my code:

/* define maze structure */

typedef struct _maze_t {
    int m, n;
    char **array;
} Maze;

void constructorArray(int m,int n)
{ 
    array = malloc(m * sizeof *array);

    for(i=0;i<m;i++){
        array[i]=(char *) malloc(n*sizeof(char)); 
    }
    array = calloc(m, sizeof *array);

    for (i=0; i<m; i++){
      array[i] = calloc(n, sizeof *(array[i]));
    }   
}
void createMaze(int ncolumn, int mlign)
{    
    int m=mlign;
    int n=ncolumn;
    int counter=0; 

    constructorArray(m,n) ;     

    char **array;            

    for(i=0;i<m;i++)
    {
        for(y=0;y<n;y++)
        {
            array[i][y]=counter;
            counter++;
        }
    }
}

int main()
{
    createMaze(100,100);    
    return 0;
}

Could someone explain to me how to do it right?

1) I see no `main()` 2) missing return type is a sign of _bad_ source of learning. — Sourav Ghosh, Nov 29 '17 at 09:23
`array=(char **) malloc(1m*sizeof(char *));` should be `array = malloc(m * sizeof *array);`. That `1m` is a syntax error. — unwind, Nov 29 '17 at 09:24
Please [read about how to ask good questions](http://stackoverflow.com/help/how-to-ask), and learn how to create a [Minimal, Complete, and Verifiable Example](http://stackoverflow.com/help/mcve). — Some programmer dude, Nov 29 '17 at 09:24
Given typos like `1m`, it appears that this code was re-typed by hand rather than copy/pasted. As such, it only approximates the code that was actually run. That means that your results will not be reliably replicated. — Tom Karzes, Nov 29 '17 at 09:28
@MichaelWalz `constructorArray(m,n)` it is valid K&R C. So if his compiler is really old... — JeremyP, Nov 29 '17 at 09:43
@JeremyP OK, your're probably right, but normally nobody should have written K&R for the last 10 (or even 20?) years. — Jabberwocky, Nov 29 '17 at 09:45
@MichaelWalz 19 years ago I was arguing at the company I worked for that we should stop using the weird parameter macros that we had to allow our code to compile in both K&R and ANSI C. So yes, people shouldn't have been using it for 20 years IMO. — JeremyP, Nov 29 '17 at 09:50

score 2 · Accepted Answer · answered Nov 29 '17 at 09:33

It seems you have some believes that are incorrect.

First, you do no correctly declare your C functions:

constructorArray(m,n)

should be:

void constructorArray(int m, int n)

Then it seems that you think a constructor will be called automatically in C, which is not so, so simply writing array[m][n] in CreateMaze won't work. You should write:

char **array;    // it will be allocated dynamically

and then have your function:

char **constructorArray(int m, int n)
{ 
    char **array= malloc(m*sizeof(char *));

    for(int i=0; i<m; i++)
        array[i]= malloc(n*sizeof(char));

    return array;
}

which you now can call as:

char **array= constructorArray(m, n);

Note: your use of the array suggests an array of ints could be more sutiable.

Create a dynamic array and initialize it

1 Answers1