aoc2021/Sources/06/06.swift

//
//  File.swift
//
//
//  Created by Max Nuding on 05.12.21.
//

import Foundation
import Runner

struct Day06: Runnable {
    let inputPath: String
    
    func run() {
        let input = try! String(contentsOfFile: inputPath)
        let internalCounters = input
            .trimmingCharacters(in: .newlines)
            .components(separatedBy: ",")
            .map { Int($0)! }
        run(fish: internalCounters, numDays: 80)
        run(fish: internalCounters, numDays: 256)
    }
    
    func run(fish: [Int], numDays: Int) {
        var tmpFish = Dictionary(grouping: fish, by: { $0 }).mapValues { $0.count }
        
        for _ in 1...numDays {
            var d = [Int:Int]()
            for f in tmpFish.keys.filter({$0 >= 0}) {
                d[f-1] = tmpFish[f]
            }
            let countPregnant = d[-1] ?? 0
            d[8] = countPregnant
            d[6] = (d[6] ?? 0) + countPregnant
            d[-1] = 0
            
            tmpFish = d
        }
        print(tmpFish.values.reduce(0, +))
    }
}