83 lines
2.6 KiB
Swift
83 lines
2.6 KiB
Swift
//
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// File.swift
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//
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//
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// Created by Max Nuding on 14.12.21.
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//
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import Foundation
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import Runner
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struct Pair: Hashable {
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let first: String.Element
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let second: String.Element
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init(_ str: String) {
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first = str.first!
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second = str.last!
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}
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init(first: String.Element, second: String.Element) {
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self.first = first
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self.second = second
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}
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}
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class Day14: Runnable {
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let inputPath: String
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required init(inputPath: String) {
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self.inputPath = inputPath
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}
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public func run() {
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let input = try! String(contentsOfFile: inputPath)
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let parts = input
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.trimmingCharacters(in: .newlines)
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.components(separatedBy: "\n\n")
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let startingPolymer = parts.first!
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let replacements = parts.last!
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.components(separatedBy: .newlines)
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.map {$0.components(separatedBy: " -> ")}
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.reduce(into: [Pair:String.Element](), {
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$0[Pair($1.first!)] = $1.last!.first!
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})
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var pairCounts = [Pair:Int]()
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var charCount = [String.Element:Int](minimumCapacity: 26)
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for i in startingPolymer.indices {
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let firstCharacter = startingPolymer[i]
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charCount[firstCharacter, default: 0] += 1
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let next = startingPolymer.index(i, offsetBy: 1)
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guard next != startingPolymer.endIndex else {
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continue
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}
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pairCounts[Pair(first: firstCharacter, second: startingPolymer[next]), default: 0] += 1
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}
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for step in 1...40 {
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let tmpPairCounts = pairCounts
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tmpPairCounts.forEach { pairCount in
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let pair = pairCount.key
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let replacement = replacements[pair]!
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pairCounts[pair]! -= pairCount.value
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pairCounts[Pair(first: pair.first, second: replacement), default: 0] += pairCount.value
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pairCounts[Pair(first: replacement, second: pair.second), default: 0] += pairCount.value
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charCount[replacement, default: 0] += pairCount.value
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}
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if step == 10 {
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printResult(charCount: charCount)
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}
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}
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printResult(charCount: charCount)
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}
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func printResult(charCount: [String.Element:Int]) {
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// Sort instead of min/max so we need to only go through the dict once
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let sorted = charCount.sorted(by: {$0.value > $1.value })
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let maxC = sorted.first!
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let minC = sorted.last!
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print(maxC.value - minC.value)
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}
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}
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