d22p2

day22/d22p2.swift

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

day22/test2.txt

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+1
+2
+3
+2024