SnakeCase.rb

=begin

Complete the function/method so that it takes CamelCase string and returns the
string in snake_case notation. Lowercase characters can be numbers. If method
gets number, it should return string.

Examples:

# returns test_controller
to_underscore('TestController')

# returns movies_and_books
to_underscore('MoviesAndBooks')

# returns app7_test
to_underscore('App7Test')

# returns "1"
to_underscore(1)

=end

# My Solution
def to_underscore(string)
  result = ""
  string.to_s.split("").each_with_index {|x,i| x == x.upcase && i != 0 && x =~ /[a-zA-Z]/ ? result += "_" + x.downcase : result += x.downcase}
  result
end

# Better Solution
def to_underscore(string)
  string.to_s.split(/(?=[A-Z])/).join('_').downcase
end

# Another Solution
def to_underscore(string)
  string.to_s.gsub(/(.)([A-Z])/, '\1_\2').downcase
end