Will's rotx

gistfile1.rb

# Build a hash of keys to use for lookup.
def build_key(x, encrypt=true)
  chars = ('a'..'z').to_a

  {}.tap do |key|
    chars.each_with_index do |char, idx|
      if(encrypt)
        key[char] = chars[(idx + x) % 26] # rotate x clicks forward
      else
        key[char] = chars[(idx - x) % 26] # rotate x clicks backwards
      end
    end
  end
end

# Rotate character using the key we built.
def rot_character(char, key)
  if char.match(/[a-z]/i)
    lookup = key[char.downcase]
    char == char.upcase ? lookup.upcase : lookup
  else
    char
  end
end

def rotx(x, string, encrypt=true)
  key = build_key(x, encrypt)

  string.split("").map do |char|
    rot_character(char, key)
  end.join
end

# Test Drive
puts "rotx(10, 'Hello, World') = #{rotx 10, 'Hello, World'}"
puts "rotx(36, 'Hello, World') = #{rotx 36, 'Hello, World'}"
puts "rotx(10, 'Rovvy, Gybvn', false) = #{rotx 10, 'Rovvy, Gybvn', false}"

Overall, I think you did a nice job. Clean and good logic. One bug that I found which would have been exposed if you had the letter "p" in your test case. If I'm a critic, I would just say that I can tell this is not written by someone with a lot of ruby experience (meaning you haven't worked on big experienced ruby codebases) but has solid fundamentals.

A couple pieces of feedback:

• You'll almost never see / need these things in seasoned ruby:
  • semicolon
  • explicit return
• Decompose your functions so each chunk of logic is its own method
  and can be unit tested.
• You had a bug where your character array did not include 'z'. Check
  the difference between two periods vs. three:

chars = ('a'..'z').to_a
chars = ('a'...'z').to_a