aoc2021/Sources/14/14.swift

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2021-12-14 16:24:15 +00:00
//
// File.swift
//
//
// Created by Max Nuding on 14.12.21.
//
import Foundation
import Runner
struct Replacement {
let from: String
let to: String
init(line: String) {
let r = line.components(separatedBy: " -> ")
from = r.first!
to = r.last!
}
func replace(pair: String) -> String.Element? { pair == from ? to.first : nil }
}
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")
var startingPolymer = parts.first!
let replacements = parts.last!
.components(separatedBy: .newlines)
.map(Replacement.init)
for step in 1...10 {
var inserts = [(String.Index, Character)]()
for i in startingPolymer.indices {
let next = startingPolymer.index(i, offsetBy: 1)
guard next != startingPolymer.endIndex else {
continue
}
var pair = startingPolymer[i]/* + startingPolymer[next]*/
let p = "\(startingPolymer[i])\(startingPolymer[next])"
for replacement in replacements {
if let c = replacement.replace(pair: p) {
inserts.append((next, c))
break
}
}
}
var tmp = startingPolymer
var count = 0
for r in inserts {
let idx = tmp.index(r.0, offsetBy: count)
tmp.insert(r.1, at: idx)
count += 1
}
startingPolymer = tmp
}
let charCounts = startingPolymer.reduce(into: [String.Element: Int](), {
$0[$1, default: 0] += 1
})
let maxC = charCounts.max(by: {$0.value < $1.value })!
let minC = charCounts.min(by: {$0.value < $1.value })!
print(maxC.value - minC.value)
}
}