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#!/usr/bin/env ruby
input = $stdin.readlines.map do |i|
i =~ /Step ([A-Z]) must be finished before step ([A-Z]) can begin./
[$2, $1]
end
steps = input.flatten.uniq.sort
prereqs = {}
workers = Array.new(5, nil)
now = 0
steps.each do |s|
prereqs[s] = []
end
input.each do |i|
prereqs[i.first] << i.last
end
until prereqs.empty? && !workers.any? do
workers.each_index do |i|
next unless workers[i]
workers[i][1] -= 1
if workers[i][1].zero?
ns = workers[i][0]
prereqs.each_key do |k|
prereqs[k].delete(ns)
end
workers[i] = nil
end
end
next_steps = prereqs.select { |k,v| v.empty? }.keys.sort
workers.each_index do |i|
unless workers[i] || next_steps.empty?
ns = next_steps.shift
time = ns.ord - 64 + 60
workers[i] = [ns, time]
prereqs.delete(ns)
end
end
now += 1
end
puts now - 1
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