Question

my row size is fixed but the column size keeps varying all the time.That’s why I am thinking to use pointers for column level.But I am not sure how to use this feature in C.Please kindly help me.

int array[rows][columns]; //row size fixed but column size is not fixed.

Answer 1

If all but one dimension of your array are fixed, which is the situation that you describe, you can avoid using arrays of pointers: you could typedef a row as int[rows], and create an array of rows, like this:

typedef int row_t[rows];

Now you can pass around 2D arrays composed of row_t arrays like this:

int total(row_t array[], int len) {
    int res = 0;
    for (int c = 0 ; c != len ; c++) {
        for (int r = 0 ; r != rows ; r++) {
            res += array[r][c];
        }
    }
    return res;
}

int main() {
    row_t *matrix = malloc(columns*sizeof(row_t));
    for (int c = 0 ; c != columns ; c++) {
        for (int r = 0 ; r != rows ; r++) {
            matrix[r][c] = r*r+c*c;
        }
    }
    printf("%d\n", total(matrix, columns));
    free(matrix);
    return 0;
}