Discussion on: Advent of Code 2019 Solution Megathread - Day 1: The Tyranny of the Rocket Equation

func fuel(forMass mass: Int) -> Int {
    return Int((Double(mass) / 3).rounded(.down) - 2)
}

func partOne() {
    var total = 0
    input.components(separatedBy: .newlines).map{ input in
        total = total + fuel(forMass: Int(input) ?? 0)
    }
    print(total)
}

func fuel(forMass mass: Int, includesFuelMass: Bool) -> Int {
    if !includesFuelMass {
        return fuel(forMass: mass)
    }

    var currentFuel = mass
    var total = 0
    while true {
        let fuels = fuel(forMass: currentFuel)
        if fuels < 0 {
            break
        }
        currentFuel = fuels
        total = total + currentFuel
    }
    return total
}

func partTwo() {
    var total = 0
    input.components(separatedBy: .newlines).map{ input in
        total = total + fuel(forMass: Int(input) ?? 0, includesFuelMass: true)
    }
    print(total)
}

partOne()
partTwo()