Problema: sistema di prenotazione aereo

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define SEATS_N 10

int main( void )
{
   srand( time(NULL) );

   int seats[ SEATS_N + 1 ] = {0};
   int scelta;
   int i, j = 0;  /* contatori prima classe / economica */
   int x;         /* per il generatore num.casuale */
   int change;    /* input in caso di cambio sistemazione */

   while ( i != SEATS_N/2 || j != SEATS_N/2 ) {

      printf( "\nPlease type 1 for \"first class\""
              "\nPlease type 2 for \"economic\": ");
      scanf( "%d", &scelta );

      if ( scelta != 1 && scelta != 2 ){
         printf( "\nErrore, riprovare.\n" );
      }
      else {

         if ( scelta == 1 ){

            x = 1 + rand() % 5;

            while ( seats[x] == 1 && i != 5 ){
               x = 1 + rand() % 5;
            }

            if ( i != 5 ) {
               seats[x] = 1;
               printf( "\nFirst class, %d", x );
               i++;
            }
            else {

               printf( "\nNo first class seats left. Would you like an economic one instead?"
                       "\n(1 yes, otherwise no): ");
               scanf( "%d", &change );

               if ( change == 1 ) {

                  x = 6 + rand() % 5;

                  while ( seats[x] == 1 ) {
                     x = 6 + rand() % 5;
                  }
                  seats[x] = 1;
                  printf( "\nEconomic, %d", x );
                  j++;
               }
               else {
                  printf( "\nNext flight leaves in 3 hours.\n" );
               }
            }
         }

         if ( scelta == 2 ){

            x = 6 + rand() % 5;

            while ( seats[x] == 1 && j != 5 ){
               x = 6 + rand() % 5;
            }

            if ( j != 5 ) {
               seats[x] = 1;
               printf( "\nEconomic, %d", x );
               j++;
            }
            else {

               printf( "\nNo economic seats left. Would you like a first class one instead?"
                       "\n(1 yes, otherwise no): ");
               scanf( "%d", &change );

               if ( change == 1 ) {

                  x = 1 + rand() % 5;

                  while ( seats[x] == 1 ) {
                     x = 1 + rand() % 5;
                  }
                  seats[x] = 1;
                  printf( "\nFirst class, %d", x );
                  i++;
               }
               else {
                  printf( "\nNext flight leaves in 3 hours.\n" );
               }
           }
         }

      }
   }

   printf( "\n\nPlane full, no seats left. Thank you.\n" );

   return 0;
}