Vim Buffer Problem

A few weeks back I tackled the following programming challenge from my colleague Josh Branchaud:

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?

Solution

Here’s my solution, also available as a Gist.

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

# vim_buffer(10000)
# => 37359001

And the test showing how it works:

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

What I Like

I like that this solution is tested! I like that it allows me to override the range minimum if I want, although I don’t remember why that was a feature.

What I Don’t Like

I don’t like that it uses to_s; type coercion feels like cheating. And I don’t like that it’s brute force. That’s fine for this problem, running ~0.042 seconds on my new (2022) computer, but it’s inelegant.

Thanks again Josh for posting these challenges to the Hashrocket team.