Assignment_06/src/main/scala/Anagrams.scala

   1 package anagrams
   2
   3 /**
   4  * Sentence anagrams generation
   5  * MSE course, T-AdvPrPa course
   6  */
   7 object Anagrams {
   8         /**
   9          * Types definitions
  10          */
  11         type Word = String
  12         type Occurrences = List[(Char, Int)]
  13         type Sentence = List[Word]
  14
  15         /**
  16          * The dictionary is simply a sequence of words.
  17          * It is predefined and obtained as a sequence using the utility method `loadDictionary`.
  18          */
  19         val dictionary: List[Word] = loadDictionary()
  20
  21         /**
  22          *  Question 1 : converts the word into its character occurrence list.
  23          *
  24          *  For instance,
  25          *  wordOccurences("abcd") gives List(('a', 1), ('b', 1), ('c', 1), ('d', 1))
  26          *  wordOccurences("aabcddd") gives List(('a', 2), ('b', 1), ('c', 1), ('d', 3))
  27          *
  28          *  Note: the upper case and lower case version of the character are treated as the
  29          *  same character, and are represented as a lower case character in the occurrence list.
  30          *  The list is sorted alphabeticaly.
  31          */
  32         def wordOccurrences(w: Word): Occurrences =
  33                 w.toLowerCase().groupBy(identity).toList.map{ case (_, letters) => (letters(0), letters.length) }.sortWith((a, b) => a._1 < b._1)
  34
  35         /**
  36          * Question 2: Valid words
  37          *
  38          * The `dictionaryByOccurrences` is a `Map` from different occurrences to a sequence of all
  39          * the words that have that occurrence count. This map serves as an easy way to obtain all the anagrams of a word given its occurrence list.
  40          */
  41         lazy val dictionaryByOccurrences: Map[Occurrences, List[Word]] =
  42                 dictionary groupBy (w => wordOccurrences(w))
  43
  44         /**
  45          * Question 3: Returns all the anagrams of a given word
  46          */
  47         def wordAnagrams(word: Word): List[Word] =
  48                 dictionaryByOccurrences get wordOccurrences(word) match {
  49                         case Some(words) => words
  50                         case None => List()
  51                 }
  52
  53         /**
  54          * Question 4: Returns all the subsets of an occurrence list
  55          */
  56
  57         /**
  58          * Generates all the subsets of a set
  59          */
  60         def combinations(occurrences: Occurrences): List[Occurrences] = ???
  61
  62         /**
  63          * Question 5: remove occurrences from x that are in y
  64          */
  65         def subtract(x: Occurrences, y: Occurrences): Occurrences = ???
  66
  67         /**
  68          * Question 6 - Generate sentence anagrams
  69          */
  70
  71         /** Converts a sentence into its character occurrence list. */
  72         def sentenceOccurrences(s: Sentence): Occurrences = ???
  73
  74         def sentenceAnagrams(sentence: Sentence): List[Sentence] = ???
  75
  76 }