69 lines
1.4 KiB
Crystal
69 lines
1.4 KiB
Crystal
require "advent"
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rlines, _, strings = input(2020, 19).partition("\n\n")
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strings = strings.lines
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rules = {} of String => String
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rlines.lines.map do |l|
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rule, _, text = l.partition(": ")
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rules[rule] = text
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end
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alias Matcher = Proc(String,Int32,Array(Int32))
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def char(c)
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->(str : String, i : Int32) { str[i]? == c ? [i+1] : [] of Int32 }
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end
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def any(ps)
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->(str : String, i : Int32) { ps.flat_map { |p| p.call(str, i) } }
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end
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def seq(ps)
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->(str : String, i : Int32) {
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base = [i]
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ps.each do |p|
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base = base.flat_map { |i| p.call(str, i) }
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end
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base
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}
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end
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def to_regex(rules, rule)
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end
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def build_rule(rules, built, rule) : Matcher
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if exists = built[rule]?
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return exists
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end
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body = rules[rule]
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return built[rule] = char body[1] if body.matches? /"."/
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branches = [] of Matcher
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top = any(branches)
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built[rule] = top
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branches.concat(body.split(" | ").map { |b| seq(b.split(" ").map { |subrule| build_rule(rules, built, subrule) }) })
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top
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end
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def part1(input)
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rules, lines = input
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matcher = build_rule(rules, {} of String => Matcher, "0")
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lines.count do |l|
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matcher.call(l, 0).includes? l.size
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end
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end
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def part2(input)
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rules, lines = input
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rules["8"] = "42 | 42 8"
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rules["11"] = "42 31 | 42 11 31"
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matcher = build_rule(rules, {} of String => Matcher, "0")
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lines.count do |l|
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matcher.call(l, 0).includes? l.size
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end
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end
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puts part1({rules,strings})
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puts part2({rules,strings})
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