具有模式或格式的C scanf

Question

i have to scanf the matrix to the dynamic 2D array (use malloc) with unknown size in this format or pattern:

%d, %d, %d ...

1, 2, 3 4, 5, 6 7, 8, 9

Therefore, every continuing line MUST be as long as the first one. If on the first line are 8 interegrs:

5, 6, 7, 8, 5, 0, 4, 5

then every next line MUST contain the same count of integers..

Then i can press CTRL+D to end standart input and continue with other calculations.

Well, i have really NO idea, how use scanf to read to dynamic array data in this format and use them. I can malloc the 2D array an use it, but I don't know, how to do this. I hope, it's easy to understand and I appreciate any help.

Thank you very much and I'm sorry for my terrible english.. Nikolas Ch.

Answer 1

scanf is NOT good for reading input where newlines are meaningful (in particular, when the difference between a newline and a space is important). That's because it treats all whitespace the same (it mostly just skips it) with nothing different between spaces and newlines.

If you need to read data where newlines are meaningful (eg, if you want to verify that each line of input has the same number of numbers, as you describe), then you really need to read entire lines (with fgets) and then read numbers out of those lines with sscanf. You may be able to use something like:

char line[2048];
int i = 0;

while (fgets(line, sizeof(line), input)) {
    char *p = line;
    int j, l;
    while (sscanf(p, "%d %n", &yourArray[i][j], &l) > 0) {
        j++;
        p += l;
        if (*p == ',') p++; }
    i++; }

Answer 2

You may use this code:

 for (int i = 0; i < column; i++)
 {
     for (int j = 0; j < row; j++)
     {
         scanf("%d", &yourArray[i][j]);
     }
 }

Answer 3

Regarding your statement: I can malloc the 2D array an use it, but I don't know, how to do this . I was not sure if you were asking help in mallocing a 2D array of numbers... If so, here is a way to create and free memory for an array of numbers. (this one is for int , but can easily be modified for any numeric type)

This, coupled with the other suggestions should provide what you need.

int ** Create2D(int **arr, int cols, int rows)
{   
    int space = cols*rows; 
    int    y;

    arr   = calloc(space, sizeof(int));
    for(y=0;y<cols;y++)
    {
        arr[y] = calloc(rows, sizeof(int)); 
    }
    return arr;
}

void free2DInt(int **arr, int cols)
{
    int i;
    for(i=0;i<cols; i++)
        if(arr[i]) free(arr[i]);
    free(arr);  
}

Use it like this:

#include <ansi_c.h>
int main(void)
{
    int **array=0, i, j;
    array = Create2D(array, 5, 4);//get the actual row/column values from reading the file once.
    for(i=0;i<5;i++)
        for(j=0;j<4;j++)
            array[i][j]=i*j; //example values for illustration
    free2DInt(array, 5);

    return 0;

}