kiru_kata.rb

require 'minitest/autorun'
require 'minitest/pride'

# Given a flat array of positive integers, partition it into three sub-arrays
# whose sums are 5, 7, and 5, respectively, or nil if doing so is impossible.
#
# The argument is the syllable (mora) count of each word in some phrase, and
# the purpose of this method is cutting (kiru) the phrase into chunks which
# satisfy the 5-7-5 rule imposed upon modern haiku.
def kiru morae
end

describe '#kiru' do
  it 'must reject obviously invalid inputs' do
    kiru([1]).must_be_nil
    kiru([6,6,6]).must_be_nil
    kiru([1, 1, 2, 3, 5, 8]).must_be_nil
  end

  it 'must handle the very simple cases' do
    kiru([1] * 17).must_equal  [[1] * 5, [1] * 7, [1] * 5]
    kiru([5,7,5]).must_equal [[5], [7], [5]]
  end

  it 'must handle slightly more complex cases' do
    kiru([1,3,1,4,1,2,2,1,2]).must_equal [[1,3,1], [4,1,2], [2,1,2]]
    kiru([5,4,2,1,1,3,1]).must_equal [[5], [4,2,1], [1,3,1]]
  end

  it 'must handle ALL THE CASES!' do
    five  = %w[11111 1112 1121 113 1211 122 131 14 2111 212 221 23 311 32 41 5]
    five.map!  { |s| s.chars.map &:to_i }
    seven = %w[1111111 111112 111121 11113 111211 11122 11131 1114 112111 11212
               11221 1123 11311 1132 1141 115 121111 12112 12121 1213 12211 1222
               1231 124 13111 1312 1321 133 1411 142 151 16 211111 21112 21121
               2113 21211 2122 2131 214 22111 2212 2221 223 2311 232 241 25 31111
               3112 3121 313 3211 322 331 34 4111 412 421 43 511 52 61 7]
    seven.map! { |s| s.chars.map &:to_i }

    five.product(seven, five).each do |morae|
      kiru(morae.flatten).must_equal morae
    end
  end

  it 'must return nil for sequences of which Master Basho would not approve' do
    kiru([3, 3, 5, 3, 3]).must_be_nil          # can't get initial 5
    kiru([1, 1, 1, 1, 2, 4, 2, 5]).must_be_nil # ditto
    kiru([2, 1, 2, 4, 2, 2, 3, 1]).must_be_nil # can't get 7
    kiru([2, 1, 2, 3, 3, 2, 2, 2]).must_be_nil # ditto
  end
end