Advent of Code 2019 - Day 1

day1.swift

import Foundation

// Code-golf version
let inputFile = URL(fileReferenceLiteralResourceName: "input.txt")
print(try! String(contentsOf: inputFile).components(separatedBy: .newlines).compactMap { Float($0) }.map { Int(($0 / 3).rounded(.down) - 2) }.reduce(0, +))

// Fancy version
typealias ModuleHopper = [Module]
typealias MassCalculations = [Float]

struct Module {
    let mass: Float
    let fuel: Int
    
    init(withMass mass: Float) {
        self.mass = mass
        self.fuel = Int((mass / 3).rounded(.down) - 2)
    }
}

func loadInput() throws -> MassCalculations {
    do {
        let inputFile = URL(fileReferenceLiteralResourceName: "input.txt")
        let rawInput = try String(contentsOf: inputFile)
        let splitFile = rawInput.components(separatedBy: .newlines)
        return splitFile.compactMap { Float($0) }
    } catch {
        throw error
    }
}

func calculateModules(from mass: MassCalculations) -> ModuleHopper {
    return mass.map { Module(withMass: $0) }
}

func calculateFuel(_ modules: ModuleHopper) -> Int {
    return modules.reduce(0, { $0 + $1.fuel })
}

func fuelCounterUpper() throws -> Int {
    do {
        let masses = try loadInput()
        let modules = calculateModules(from: masses)
        return calculateFuel(modules)
    } catch {
        throw error
    }
}

if let fuelNeeded = try? fuelCounterUpper() {
    print("Total fuel units required: \(fuelNeeded)")
}