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advent-of-code/2018/ruby/day_09.rb

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Node = Struct.new(*%i[ value next prev ]) do
def to_s
out = [value]
current = self
loop do
current = current.next
break if current == self
out << current.value
end
out.join(" ")
end
end
ARGF.read.chomp =~ /(\d+) players; last marble is worth (\d+) points/
num_players = $1.to_i
num_marbles = $2.to_i * 100
current = Node.new(0, nil, nil)
current.next = current.prev = current
current_player = 0
scores = Array.new(num_players, 0)
(1...num_marbles).each do |marble|
if marble % 23 == 0
scores[current_player] += marble
7.times { current = current.prev }
scores[current_player] += current.value
current.next.prev = current.prev
current.prev.next = current.next
current = current.next
else
current = current.next
current.next = Node.new(marble, current.next, current)
current = current.next
current.next.prev = current
end
# puts "[#{current_player + 1}] #{current}"
puts marble if marble % 100000 == 0
current_player = (current_player + 1) % num_players
end
p scores.max