/* Given a set of consecutive characters, find a hash expression that
   would produce the desired symbols.

   Result:
   'A' * 24 % 50 = '\n'
   'B' * 24 % 50 = '"'
   'D' * 24 % 50 = ' '
*/

#include<stdio.h>

/* List of consecutive unused characters from prime_cut2.c */
static const char *kKeySets[4] =
{
   "123",
   "5678",
   "ABCD",
   "wxyz",
};

/* Hash function. */
static int Hash(char input, int p, int q)
{
   return input * p % q;
}

/* Try hashing a set of keys to the desired symbols. */
static void TryKeySet(const char *keys)
{
   int p, q, v, coverage;
   const char *k;

   for(p = 0; p < 1000; p++)
   {
      for(q = 1; q < 1000; q++)
      {
         coverage = 0;
         for(k = keys; *k; k++)
         {
            v = Hash(*k, p, q);
            if( v == ' ' ) coverage |= 1;
            if( v == '\n' ) coverage |= 2;
            if( v == '"' ) coverage |= 4;
         }
         if( coverage == 7 )
         {
            printf("keys = %s, p = %d, q = %d:", keys, p, q);
            for(k = keys; *k; k++)
               printf("\t%d->%d", *k, Hash(*k, p, q));
            putchar('\n');
         }
      }
   }
}

int main(void)
{
   int k;

   for(k = 0; k < 4; k++)
      TryKeySet(kKeySets[k]);
   return 0;
}