2つ目は再帰

test_chop.rb

#!/usr/bin/env ruby
# http://codekata.com/kata/kata02-karate-chop/

require 'test/unit'

def chop(target, values)
  index = values.length / 2

  return index if values[index] == target
  return -1    if index.zero?

  if values[index] > target
    chop(target, values[0..index - 1])
  else
    result = chop(target, values[index..values.length - 1])
    return -1 if result == -1
    index + result
  end
end

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(-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

ひどいコードだけどテストは通る

ひどすぎて泣きそう