Non-decreasing sequence generation

Script.c

#include <stdio.h>
#include <stdlib.h>

static int N;
static int counter = 0;
static int do_io = 0;

static void helper (int idx, int pos, int* triplet);

int
main (int argc, char* argv[]) {
    if (argc != 2 && argc != 3) {
        printf ("USAGE: ./generate N [do_io flag (defaults to 0 as no_do_io)]\n");
        exit (1);
    }
    sscanf (argv[1], "%d", &N);
    if (argc == 3)
        sscanf (argv[2], "%d", &do_io);
    int triplet[N];
    for (int i = 0; i < N; i++) {
        triplet[i] = -1;
    }
    for (int i = 0; i < 10; i++)
        helper (i, 0, triplet);
    printf ("\n# count of results: %d\n", counter);
}

static void
helper (int idx, int pos, int* triplet) {
    triplet[pos] = idx;
    if (pos >= N - 1) {
        if ((counter++) % 10 == 0 && counter != 1) {
            if (do_io)
                printf ("\n");
        }
        if (do_io) {
            printf ("{");
            for (int i = 0; i < N; i++) {
                printf ("%d", triplet[i]);
                if (i < N - 1)
                    printf (", ");
            }
            printf ("}, ");
        }
    } else {
        for (int i = idx; i < 10; i++) {
            helper (i, pos + 1, triplet);
        }
    }
    triplet[pos] = -1;
}