Vim Buffer

vim_buffer.rb

# Week 2 - Vim Buffer: I open up a new Vim buffer and type all the
# numbers 1 to 10,000, separated by spaces. Then, my cat walks on the keyboard
# and somehow activates a substitution command that replaces all the '0’ digits
# (zeros) with spaces. If I now sum up all the numbers in the buffer, as
# delineated by spaces, what is the total?

def vim_buffer(start = 1, limit)
  (start..limit).flat_map { |num| num.to_s.gsub('0', ' ').split }.map(&:to_i).reduce(:+)
end

# vim_buffer(10000)
# => 37359001

require 'minitest/autorun'

class TestVimBuffer < Minitest::Test
  def test_ten
    assert_equal(46, vim_buffer(10))
  end

  def test_eleven
    assert_equal(57, vim_buffer(11))
  end

  def test_ten_twelve
    assert_equal(69, vim_buffer(12))
  end
end