aoc2021/Sources/07/07.swift

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

import Foundation
import Runner

struct Day07: Runnable {
    let inputPath: String
    
    func run() {
        let input = try! String(contentsOfFile: inputPath)
        let horizontalPositions = input
            .trimmingCharacters(in: .newlines)
            .components(separatedBy: ",")
            .map { Int($0)! }
        runA(horizontalPositions: horizontalPositions)
        runB(horizontalPositions: horizontalPositions)
    }
    
    func runA(horizontalPositions: [Int]) {
        let median = horizontalPositions.sorted()[horizontalPositions.count / 2]
        let distancesToMedian = horizontalPositions.map { abs(median - $0) }
        let toalFuel = distancesToMedian.reduce(0,+)
        print(toalFuel)
    }
    
    func runB(horizontalPositions: [Int]) {
        let average = Double(horizontalPositions.reduce(0, +)) / Double(horizontalPositions.count)
        let roundedDown = Int(floor(average))
        let roundedUp = Int(ceil(average))
        let fuelForRoundedDown = fuelConsumptionFor(horizontalPositions: horizontalPositions, toPosition: roundedDown)
        let fuelForRoundedUp = fuelConsumptionFor(horizontalPositions: horizontalPositions, toPosition: roundedUp)
        print(min(fuelForRoundedDown, fuelForRoundedUp))
    }
    
    func fuelConsumptionFor(horizontalPositions: [Int], toPosition targetPos: Int) -> Int {
        horizontalPositions.map { fuelConsumptionFor(numSteps: abs(targetPos - $0)) }.reduce(0,+)
    }
    
    func fuelConsumptionFor(numSteps: Int) -> Int {
        let dv = Double(numSteps)
        return Int((pow(dv, 2) + dv) / 2.0)
    }
}