There are many ways to approach this task. The key is making it work regardless of small variations in input format. That is where strtol excels. It also provides much better error analysis on a conversion failure than most.
The example below simply reads your data into an array by reading a line-at-a-time and parsing that line into values with strtol. Take a look and give it a try. Note the functions below dealing with allocating memory are just to keep the body of the code clean so you can hopefully follow the logic easier without all the allocation validation checks filling up main(). Good luck:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <errno.h>
#define ROWS 3
#define COLS 3
#define MAXC 256
long xstrtol (char *p, char **ep, int base);
void *xcalloc (size_t n, size_t s);
void *xrealloc_sp (void *p, size_t sz, size_t *n);
void *xrealloc_dp (void **p, size_t *n);
int main (void) {
char line[MAXC] = {0}; /* line buffer for fgets */
char *p, *ep; /* pointers for strtol */
int **array = NULL; /* array of values */
size_t row = 0, col = 0, nrows = 0; /* indexes, number of rows */
size_t rmax = ROWS, cmax = COLS; /* row/col allocation size */
/* allocate ROWS number of pointers to array of int */
array = xcalloc (ROWS, sizeof *array);
/* read each line in file */
while (fgets(line, MAXC, stdin))
{
p = ep = line; /* initize pointer/end pointer */
col = 1; /* start col at 1, store ncols in 0 */
cmax = COLS; /* reset cmax for each row */
/* allocate COLS number of int for each row */
array[row] = xcalloc (COLS, sizeof **array);
/* convert each string of digits to number */
while (errno == 0)
{
array[row][col++] = (int)xstrtol (p, &ep, 10);
if (col == cmax) /* if cmax reached, realloc array[row] */
array[row] = xrealloc_sp (array[row], sizeof *array[row], &cmax);
/* skip delimiters/move pointer to next digit */
while (*ep && *ep != '-' && (*ep < '0' || *ep > '9')) ep++;
if (*ep)
p = ep;
else /* break if end of string */
break;
}
array[row++][0] = col; /* store ncols in array[row][0] */
/* realloc rows if needed */
if (row == rmax) array = xrealloc_dp ((void **)array, &rmax);
}
nrows = row; /* set nrows to final number of rows */
printf ("\n the simulated 2D array elements are:\n\n");
for (row = 0; row < nrows; row++) {
for (col = 1; col < (size_t)array[row][0]; col++)
printf (" %4d", array[row][col]);
putchar ('\n');
}
putchar ('\n');
/* free all allocated memory */
for (row = 0; row < nrows; row++)
free (array[row]);
free (array);
return 0;
}
/** a simple strtol implementation with error checking.
* any failed conversion will cause program exit. Adjust
* response to failed conversion as required.
*/
long xstrtol (char *p, char **ep, int base)
{
errno = 0;
long tmp = strtol (p, ep, base);
/* Check for various possible errors */
if ((errno == ERANGE && (tmp == LONG_MIN || tmp == LONG_MAX)) ||
(errno != 0 && tmp == 0)) {
perror ("strtol");
exit (EXIT_FAILURE);
}
if (*ep == p) {
fprintf (stderr, "No digits were found\n");
exit (EXIT_FAILURE);
}
return tmp;
}
/** xcalloc allocates memory using calloc and validates the return.
* xcalloc allocates memory and reports an error if the value is
* null, returning a memory address only if the value is nonzero
* freeing the caller of validating within the body of code.
*/
void *xcalloc (size_t n, size_t s)
{
register void *memptr = calloc (n, s);
if (memptr == 0)
{
fprintf (stderr, "%s() error: virtual memory exhausted.\n", __func__);
exit (EXIT_FAILURE);
}
return memptr;
}
/** reallocate array of type size 'sz', to 2 * 'n'.
* accepts any pointer p, with current allocation 'n',
* with the type size 'sz' and reallocates memory to
* 2 * 'n', updating the value of 'n' and returning a
* pointer to the newly allocated block of memory on
* success, exits otherwise. all new memory is
* initialized to '0' with memset.
*/
void *xrealloc_sp (void *p, size_t sz, size_t *n)
{
void *tmp = realloc (p, 2 * *n * sz);
#ifdef DEBUG
printf ("\n reallocating '%zu' to '%zu', size '%zu'\n", *n, *n * 2, sz);
#endif
if (!tmp) {
fprintf (stderr, "%s() error: virtual memory exhausted.\n", __func__);
exit (EXIT_FAILURE);
}
p = tmp;
memset (p + *n * sz, 0, *n * sz); /* zero new memory */
*n *= 2;
return p;
}
/** reallocate memory for array of pointers to 2 * 'n'.
* accepts any pointer 'p', with current allocation of,
* 'n' pointers and reallocates to 2 * 'n' pointers
* intializing the new pointers to NULL and returning
* a pointer to the newly allocated block of memory on
* success, exits otherwise.
*/
void *xrealloc_dp (void **p, size_t *n)
{
void *tmp = realloc (p, 2 * *n * sizeof tmp);
#ifdef DEBUG
printf ("\n reallocating %zu to %zu\n", *n, *n * 2);
#endif
if (!tmp) {
fprintf (stderr, "%s() error: virtual memory exhausted.\n", __func__);
exit (EXIT_FAILURE);
}
p = tmp;
memset (p + *n, 0, *n * sizeof tmp); /* set new pointers NULL */
*n *= 2;
return p;
}
Compile
gcc -Wall -Wextra -Ofast -o bin/array_ukn_size array_ukn_size.c
Input
$ cat ../dat/10by10.txt
0 1 2 3 4 5 6 7 8 9
10 11 12 13 14 15 16 17 18 19
20 21 22 23 24 25 26 27 28 29
30 31 32 33 34 35 36 37 38 39
40 41 42 43 44 45 46 47 48 49
50 51 52 53 54 55 56 57 58 59
60 61 62 63 64 65 66 67 68 69
70 71 72 73 74 75 76 77 78 79
80 81 82 83 84 85 86 87 88 89
90 91 92 93 94 95 96 97 98 99
Output
$ ./bin/array_ukn_size <../dat/10by10.txt
the simulated 2D array elements are:
0 1 2 3 4 5 6 7 8 9
10 11 12 13 14 15 16 17 18 19
20 21 22 23 24 25 26 27 28 29
30 31 32 33 34 35 36 37 38 39
40 41 42 43 44 45 46 47 48 49
50 51 52 53 54 55 56 57 58 59
60 61 62 63 64 65 66 67 68 69
70 71 72 73 74 75 76 77 78 79
80 81 82 83 84 85 86 87 88 89
90 91 92 93 94 95 96 97 98 99
