Ytukyg

So i have a 20 x 20 array, and its all filled with -1.
I also have an input.txt which contains some numbers, for example :

2,3

5,6

How can i fill my array so that array[0][0] will be 2,
array[0][1] will be 3, array[1][0] will be 5, array[1][1] will be 6, and every other element will be -1.

I've tried with a for loop thats using fscanf until there is a new line, but that won't work.

I've tried with a for loop thats using fscanf until there is a new line, but that won't work.

Variations on fscanf(in, "%d,%dn", &x, &y), as in OP's prior question, fail to detect end-of-line. The 'n' in the format will match any white-space on input including 'n', ' ', 't',etc.

Simplistic usage of fscanf(..., "%d",...) can readily fail as "%d" will consume all leading white-space with no discrimination between 'n' and other white-spaces.

How can i fill my array ...

Although possible to use fscanf() to solve this task, consider fgets(), strtol().

The best approach is to use fgets() to reach a line: all characters up to and including the one final 'n'. Then use strtol(), strtoll(), etc. to read the integers.

long integers and spacing each needs reasonable less than 21 characters. To accommodate extra leading zeros spacing, etc, let use 2x the anticipated size needs.

#define CHAR_PER_NUMBER 21

#define NUM_PER_LINE 20

#define LINE_NUM 20

#define LINE_SIZE (NUM_PER_LINE * CHAR_PER_NUMBER * 2)



long array[LINE_NUM][NUM_PER_LINE];



// read data

for (int i = 0; i < LINE_NUM; i++) {

  char buf[LINE_SIZE + 1]; // +1: room for the appended the null character

  if (fgets(buf, sizeof buf, in) == NULL) {

    buf[0] = '';

  }

  // Now parse the line

  char *p = buf;

  for (int j = 0; j < NUM_PER_LINE; j++) {

    char *endptr;

    array[i][j] = strtol(p, &endptr, 10);

    if (p == endptr) {

      array[i][j] = -1; // no conversion  

    }

    p = endptr; // advance to the next number

  }

}

Additional concerns including handling pathological long lines, values outside the long range, I/O error handling and efficiency details.

Should input consists of text representing floating-point, a more generous max size per value is warranted.

Try using "end of file"(eof), where m and n are the rows and columns

for (i = 0; i < m && !feof(input); i++)

  for (j = 0; j < n && !feof(input); j++)

  fscanf(input, "%f", &a[i][j]);

If the size of the array (m and n) is also given in the file write an if condition before

if (!feof(input))

  fscanf(input, "%d %d", &m, &n);

for (i = 0; i < m && !feof(input); i++)

      for (j = 0; j < n && !feof(input); j++)

      fscanf(input, "%f", &a[i][j]);