31 lines
1.1 KiB
Swift
31 lines
1.1 KiB
Swift
import Foundation
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func readInput(_ filePath: String) throws -> [Int] {
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return try String(contentsOfFile: filePath, encoding: .ascii)
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.split(separator: "\n").compactMap { Int($0) }
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}
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func haggle(_ seeds: [Int]) -> [[Int]: [Int: Int]] {
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var bananas: [[Int]: [Int: Int]] = [:]
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for (monkey, seed) in seeds.enumerated() {
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var prevs = [Int.min, Int.min, Int.min, Int.min]
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var lastPrice = seed
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for _ in 0..<2000 {
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var price = ((lastPrice << 6) ^ lastPrice) & 16777215
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price = ((price >> 5) ^ price)
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price = ((price << 11) ^ price) & 16777215
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prevs[0] = prevs[1]; prevs[1] = prevs[2]; prevs[2] = prevs[3]
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prevs[3] = (price % 10) - (lastPrice % 10)
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lastPrice = price
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if let _ = bananas[prevs, default: [:]][monkey] { continue }
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bananas[prevs, default: [:]][monkey] = price % 10
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}
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}
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return bananas
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}
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let seeds = try readInput(CommandLine.arguments[1])
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let bananas = haggle(seeds)
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print(bananas.values.map { $0.values.reduce(0, +) }.max() ?? "ERROR")
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