#! /usr/bin/env ruby

# Finds answer to following puzzle
#
# There are one thousand candles on the altar and one thousand priests
# in the temple. Their god asks the first priest to go and light all
# the candles. Then he has the second priest go to every second candle
# and put it out."
#
# The third goes to every third candle and, if it is not burning, he
# lights it, and if it is lit, he puts it out."
#
# The fourth priest does this to every fourth candle, and so on. After
# the process is completed with the thousandth priest, how many
# candles are not lit?"

candles = []

(1..1000).each do |priest|
  (0...1000).step(priest) do |candle|
    candles[candle] = !candles[candle]
  end
end

puts "#{candles.select{|c|c}.count} candles lit"
puts "#{candles.select{|c|!c}.count} candles unlit"