Kata 2

kata2.rb

def chop(target, ordered_array)
  # Wrap ordered array with an array if it has not been wrapped
  ordered_array = [ordered_array, 0] if !ordered_array[0].is_a?(Array)
  sub_array = ordered_array[0]
  total_sliced_from_left = ordered_array[1]

  # no matches found
  return -1 if sub_array.empty? || sub_array.size == 1 && sub_array[0] != target

  middle = sub_array.size / 2
  middle_element = sub_array[middle]

  if target == middle_element && sub_array.size == 1
    return total_sliced_from_left
  end

  if middle_element < target
    size_before = sub_array.size
    sub_array = sub_array[middle + 1..sub_array.size]
    size_now = sub_array.size
    total_sliced_from_left += size_before - size_now
  elsif middle_element == target
    size_before = sub_array.size
    sub_array = sub_array[middle..sub_array.size]
    size_now = sub_array.size
    total_sliced_from_left += size_before - size_now
  else
    sub_array = sub_array[0..middle - 1]
  end

  ordered_array = [sub_array, total_sliced_from_left]
  chop(target, ordered_array)
end

tc-kata2.rb

require './kata2.rb'

require 'test/unit'

class TestChop < Test::Unit::TestCase

  def test_chop
    assert_equal(-1, chop(3, []))
    assert_equal(-1, chop(3, [1]))
    assert_equal(0,  chop(1, [1]))

    assert_equal(0,  chop(1, [1, 3, 5]))
    assert_equal(1,  chop(3, [1, 3, 5]))
    assert_equal(2,  chop(5, [1, 3, 5]))

    assert_equal(-1, chop(0, [1, 3, 5]))
    assert_equal(-1, chop(2, [1, 3, 5]))
    assert_equal(-1, chop(4, [1, 3, 5]))
    assert_equal(-1, chop(6, [1, 3, 5]))

    assert_equal(0,  chop(1, [1, 3, 5, 7]))
    assert_equal(1,  chop(3, [1, 3, 5, 7]))
    assert_equal(2,  chop(5, [1, 3, 5, 7]))
    assert_equal(3,  chop(7, [1, 3, 5, 7]))
    assert_equal(7,  chop(22,[1, 3, 5, 7, 8, 10, 11, 22, 23]))
    assert_equal(6,  chop(15,[1, 3, 5, 7, 8, 10, 15, 22, 23]))
    assert_equal(4,  chop(5, [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31]))
    assert_equal(-1, chop(0, [1, 3, 5, 7]))
    assert_equal(-1, chop(2, [1, 3, 5, 7]))
    assert_equal(-1, chop(4, [1, 3, 5, 7]))
    assert_equal(-1, chop(6, [1, 3, 5, 7]))
    assert_equal(-1, chop(8, [1, 3, 5, 7]))
  end

end