advent_day_1.rb

# http://adventofcode.com/day/1 - part 1
#
# instructions - String containing coded instructions for moving up a floor with
# "(" and down a floor with ")"
# Starting ground floor numbered zero is assumed.
#
# Returns an integer value for the expected floor.
def ups_and_downs(instructions)
  instructions.count("(") - instructions.count(")")
end

# http://adventofcode.com/day/1 - part 2
#
# instructions - String containing coded instructions for moving up a floor with
# "(" and down a floor with ")"
# Starting ground floor numbered zero is assumed.
# Also assuming that the first character of the instructions is considered
# instruction #1 (not zero).
#
# Returns an integer value for the first instruction that leads to the basement
# (floor -1), or nil if it did not ever lead there.
def in_the_basement(instructions)
  steps = instructions.split("")

  floor = 0

  steps.each_with_index do |step, i|
    if step == "("
      floor += 1
    elsif step == ")"
      floor -= 1
    end

    return i + 1 if floor == -1
  end
end