65 lines
1.2 KiB
Swift
65 lines
1.2 KiB
Swift
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import Foundation
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let input = """
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9 ORE => 2 A
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8 ORE => 3 B
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7 ORE => 5 C
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3 A, 4 B => 1 AB
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5 B, 7 C => 1 BC
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4 C, 1 A => 1 CA
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2 AB, 3 BC, 4 CA => 1 FUEL
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"""
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struct Chemical {
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let name: String
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let amount: Int
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}
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struct Reaction {
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let product: Chemical
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let educts: [Chemical]
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}
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var reactions: [String: Reaction] = [:]
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let scanner = Scanner(string: input)
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func parseChemical() -> Chemical? {
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guard let amount = scanner.scanInt(),
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let name = scanner.scanCharacters(from: .letters) else {
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return nil
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}
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return Chemical(name: name, amount: amount)
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}
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func parseReaction() -> Reaction? {
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var educts: [Chemical] = []
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repeat {
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guard let chemical = parseChemical() else {
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return nil
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}
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educts.append(chemical)
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} while scanner.scanString(",") != nil
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guard scanner.scanString("=>") != nil else {
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return nil
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}
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guard let product = parseChemical() else {
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return nil
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}
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return Reaction(product: product, educts: educts)
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}
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while !scanner.isAtEnd {
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guard let reaction = parseReaction() else {
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fatalError()
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}
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reactions[reaction.product.name] = reaction
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}
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