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59 lines
1.3 KiB
59 lines
1.3 KiB
require "strscan"
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# def evaluate(input)
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# while input.include?(?()
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# input = input.gsub(/\((?~[()])+\)/) {|m| evaluate(m[1..-2]) }
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# end
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# # part one
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# # ss = StringScanner.new(input)
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# # n = ss.scan(/\d+/).to_i
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# # until ss.eos?
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# # case
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# # when ss.scan(/\s*\+\s*(\d+)/)
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# # n += ss.captures[0].to_i
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# # when ss.scan(/\s*\*\s*(\d+)/)
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# # n *= ss.captures[0].to_i
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# # else
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# # fail
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# # end
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# # end
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# # n
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# while input.include?(?+)
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# input = input.gsub(/\d+\s*\+\s*\d+/) {|m| eval(m) }
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# end
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# while input.include?(?*)
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# input = input.gsub(/\d+\s*\*\s*\d+/) {|m| eval(m) }
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# end
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# input.to_i
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# end
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def evaluate(input)
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stack = [->(x) { x }]
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ss = StringScanner.new(input)
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until ss.eos?
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ss.scan(/\s*/)
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stack << case
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when n = ss.scan(/\d+/)
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stack.pop[n.to_i]
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when ss.scan(/\+/)
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->(x) { stack.pop + x }
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when ss.scan(/\*/)
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->(x) { stack.pop * x }
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when ss.scan(/\(/)
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->(x) { x }
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when ss.scan(/\)/)
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n = stack.pop
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stack.pop[n]
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else
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fail
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end
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end
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stack.pop
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end
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p ARGF.read.split("\n").map {|line| evaluate(line) }.sum
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