[2021][ruby][14.x]

pull/2/head
Alpha Chen 3 years ago
parent b7e00339a3
commit 8e38040c04

@ -0,0 +1,41 @@
template, rules = ARGF.read.split("\n\n")
template = template.chars
rules = rules.scan(/(\w{2}) -> (\w)/).to_h
# polymer = template
# 10.times do
# polymer = polymer.each_cons(2).flat_map {|a,b|
# [a, rules.fetch("#{a}#{b}")]
# } << polymer.last
# end
# min, max = polymer.tally.values.minmax
# p max - min
tally = Hash.new {|h,k|
polymer, steps = k
new_elements = polymer.each_cons(2).map(&:join).map { rules.fetch(_1) }
h[k] = case steps
when 1
(polymer + new_elements).tally
when (2..)
initial = new_elements.tally.transform_values { -_1 }
polymer.zip(new_elements)
.flatten[0..-2]
.each_cons(2)
.map { h[[_1, steps-1]] }
.inject(initial) {|final,tally| final.merge(tally) { _2 + _3 } }
else
fail
end
}
final = tally[[template, 40]]
# correct for internal elements being double-counted
template[1..-2].each do
final[_1] -= 1
end
min, max = final.values.minmax
p max - min
Loading…
Cancel
Save