Today's Kata 10-29-2015

all_the_same_digit_numbers.rb

# Today's kata:
# Given a 3 or 4 digit number with distinct digits, return a sorted array of all the unique numbers that can be formed with those digits.
# ie, given 123, return [123, 132, 213, 231, 312, 321]

def same_digit_numbers(initial_num)
  initial_num.to_s.split('').permutation.map {|e| e.join.to_i }.uniq.sort
end

def same_digit_numbers(initial_num)
  num_string = initial_num.to_s
  num_length = num_string.length

  index_arrays(num_length).map do |index_array|
    index_array.map { |index| num_string[index] }.join.to_i
  end.uniq.sort
end

def index_arrays(num)
  fold_up( tree_down( num.times.to_a ) )
end

def tree_down(indices)
  if indices.size == 1
    indices.pop
  else
    indices.map { |e| [e, tree_down(indices - [e])] }
  end
end

def flat?(a)
  a == a.flatten
end

def fold_up(full_nested)
  if flat?( full_nested[-1] )
    full_nested
  else
    fold_up( full_nested.reduce [] { |result, e| result + fold(e) } )
  end
end

def fold(part_nested)
  part_nested[-1].map { |e| part_nested[0..-2] + e }
end

gem 'minitest'
require 'minitest/autorun'

class TestRev < Minitest::Test

  def test_permute
    assert_equal [123, 132, 213, 231, 312, 321], same_digit_numbers(123)
  end

  def test_four_digits
    assert_equal [1234, 1243, 1324, 1342, 1423, 1432, 2134, 2143, 2314, 2341, 2413, 2431, 3124, 3142, 3214, 3241, 3412, 3421, 4123, 4132, 4213, 4231, 4312, 4321], same_digit_numbers(1234)
  end

  def test_for_another_number
    assert_equal [234, 243, 324, 342, 423, 432], same_digit_numbers(243)
  end

  def test_for_duplication
    assert_equal [111], same_digit_numbers(111)
  end

  def test_for_digit_duplication
    assert_equal [122, 212, 221], same_digit_numbers(212)
  end
end

+1 nice!!!