aoc2021/Sources/14/14.swift

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