How to find an array of all the words in json that can be made by rearranging these letters(Ruby)-CodePudding

I am new to ruby. How do I write a function that takes a find method that accepts a lower case and the find should return an array of all the words in dic.json that can be made by rearranging these letters. So if I input "ab" then the output should be ["ab", "ba"] from the JSON file below.

dic.json

[
"ab",
"ba",
"abc",
"acb",
"bac",
"bca",
"cab",
"cba"
]

This is what have so far

I used File read to access the JSON file and I have a function that can find permutations but I am not sure how to connect the two functions.

class LetterLocater
  def get_file_contents
    return File.read('dictionary.json').split
  end

   def permutation(letters)
    return [''] if letters.empty?

    chrs = letters.chars
    (0...letters.size).flat_map { |i|
      chr, rest = letters[i], letters[0...i]   letters[i 1..-1]
      permutation(rest).map { |sub|
        chr   sub
      }
    }
  end
end

a = LetterLocater.new
puts a.permutation(gets.chomp)                                                                                                                                       ```

CodePudding user response：

Instead of creating all permutations for various inputs, you could also group the words from the dictionary once by sorting their letters:

def sorted(str)
  str.chars.sort.join
end

# assume this was read from the JSON file
dict = %w[ab ba abc acb bac bca cab cba]

lookup_hash = dict.group_by { |word| sorted(word) }
#=> {
#     "ab"  => ["ab", "ba"],
#     "abc" => ["abc", "acb", "bac", "bca", "cab", "cba"]
#   }

Now it's almost trivial to find the permutations. You just have to fetch the values for the sorted input:

input = gets.chomp
puts lookup_hash[sorted(input)]

CodePudding user response：

In Ruby there is already Array#permutation that you can use to calculate all possible words.

letters = "ab" # example
permutations = letters.split(//).permutation.map(&:join)
#=> ["ab", "ba"]

And then there is 'Array#&' that returns only elements from an array that are present in another array.

words = ["ab", "ba", "abc", "acb", "bac", "bca", "cab", "cba"]
words & permutations
#=> ["ab", "ba"]

And you can use JSON.load(File.open('dictionary.json')) to load the JSON file into a Ruby array – as Schwern already wrote in his comment.

Now let's combine all these methods into one class

require 'json'

class LetterLocater
  attr_reader :words

  def initialize(dictionary)
    @words = JSON.load(File.open('dictionary.json'))
  end

  def permutation(letters)
    permutations = letters.split(//).permutation.map(&:join)
    words & permutations
  end
end

ll = LetterLocater.new('dictionary.json')

ll.permutation('ab')
#=> ["ab", "ba"]
ll.permutation('abc')
#=> ["abc", "acb", "bac", "bca", "cab", "cba"]

CodePudding user response：

def find_permutations_in_array(arr, str)
  chars = str.chars.sort
  arr.inject([]) do |res, word|
    res << word if word.size == str.size && word.chars.sort == chars
    res
  end
end