# include <stdio.h>
# include <string.h>
//
//  Based on program 10.10, Stephen Kochan, Programming in C.
//
struct entry
{
  char word[15];
  char definition[50];
};

int main ( int argc, char *argv[] );
int compareStrings ( const char s1[], const char s2[] );
int lookup ( const struct entry dictionary[], const char search[], const int entries );

int main ( int argc, char *argv[] )
{
  const struct entry dictionary[100] = 
  {
    { "aardvark", "a burrowing African mammal"        },
    { "abyss",    "a bottomless pit"                  },
    { "acumen",   "mentally sharp, keen"              },
    { "addle",    "to become confused"                },
    { "aerie",    "a high nest"                       },
    { "affix",    "to append or attach"               },
    { "agar",     "a jelly made from seaweed"         },
    { "ahoy",     "a nautical call of greeting"       },
    { "aigrette", "an ornamental cluster of feathers" },
    { "ajar",     "partially open"                    }
  };
  char word[81];
  int entries = 10;
  int entry;
//
//  If the user didn't enter a word, ask for it.
//
  if ( argc < 2 )
  {
    printf ( "Enter word: " );
    scanf ( "%14s", word );
  }
//
//  Otherwise, copy the command line argument into WORD.
//
  else
  {
    strcpy ( word, argv[1] );
  }

  entry = lookup ( dictionary, word, entries );

  if ( entry != -1 )
  {
    printf ( "The word \"%s\" means %s.\n", word, dictionary[entry].definition );
  }
  else
  {
    printf ( "Sorry, the word \"%s\" is not in my dictionary.\n", word );
  }
  return 0;
}

int compareStrings ( const char s1[], const char s2[] )
{
  int i = 0, answer;

  while ( s1[i] == s2[i] && s1[i] != '\0' && s2[i] != '\0' )
  {
    i = i + 1;
  }
  if ( s1[i] < s2[i] )
  {
    answer = -1;
  }
  else if ( s1[i] == s2[i] )
  {
    answer = 0;
  }
  else
  {
    answer = +1;
  }
  return answer;
}

int lookup ( const struct entry dictionary[], const char search[], const int entries )
{
  int low = 0;
  int high = entries - 1;
  int mid;
  int result;

  while ( low <= high )
  {
    mid = ( low + high ) / 2;
    result = compareStrings ( dictionary[mid].word, search );

    if ( result == -1 )
    {
      low = mid + 1;
    }
    else if ( result == 0 )
    {
      return mid;
    }
    else
    {
      high = mid - 1;
    }
  }
  return -1;
}