reverse.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/types.h>
#include "linked_list_lib.h"


unsigned int foo(unsigned int n, unsigned int r)
{
    if (n > 0)
        return (n % r + foo(n / r, r));
    else
        return 0;
}

// int fun(int x, int y) 
// {
//   if (x == 0)
//     return y;
//   return fun(x - 1,  x + y);
// } 


int fun(int n){
  int x = 1, k;
  if (n == 1) 
    return x;
  for (k = 1; k < n; ++k)
     x = x + fun(k) * fun(n - k);
  return x;
}




int main(int argc, char *argv[]) {

  int a = fun(4);

  printf("%d\n", a);
  exit(1);

  if (argc >= 4) {
    fprintf(stderr, "usage: reverse <input> <output>\n");
    exit(EXIT_FAILURE);
  }

  char *input_file_name = argv[1];
  char *output_file_name = argv[2];

  FILE *input_stream = argc <= 1 ? stdin : fopen(input_file_name, "r");
  FILE *output_stream = argc <= 2 ? stdout : fopen(output_file_name, "rw");

  if (!input_stream || !output_stream) {
    fprintf(stderr, "reverse: cannot open file '%s'\n", !input_stream ? input_file_name : output_file_name);
    exit(EXIT_FAILURE);
  }

  struct stat input_file_stat, output_file_stat;
  if (fstat(fileno(input_stream), &input_file_stat) == -1 || fstat(fileno(output_stream), &output_file_stat) == - 1) {
    fprintf(stderr, "reverse: fstat error\n");
    exit(EXIT_FAILURE);
  }
  
  if (input_file_stat.st_ino == output_file_stat.st_ino) {
    fprintf(stderr, "reverse: input and output file must differ\n");
    exit(EXIT_FAILURE);
  }

  size_t buffer_size = sizeof(char *);
  struct ListNode *linked_list_a_head = NULL;
  write_stream_to_ll(&linked_list_a_head, input_stream, buffer_size);
  
  write_ll_to_stream(output_stream, linked_list_a_head);

  free_ll_nodes(linked_list_a_head);
  fclose(input_stream);
  fclose(output_stream);
}