ApartmentsTask.swift

struct ApartmentPlacement: Equatable {
    let entrance: Int
    let floor: Int
    let location: Int
}

func calculateApartmentPlacement(for apartmentNumber: Int, totalEntrances: Int, totalFloors: Int) -> ApartmentPlacement? {
    let apartmentIndex = apartmentNumber - 1
    guard totalEntrances > 0, totalFloors > 0 else {
        return nil
    }

    let totalLocations = 4
    let totalApartmentsPerEntrance = totalFloors * totalLocations
    let totalApartments = totalEntrances * totalApartmentsPerEntrance

    guard (0..<totalApartments).contains(apartmentIndex) else {
        return nil
    }

    let seekedEntranceIndex = apartmentIndex / totalApartmentsPerEntrance
    let seekedFloorIndex = apartmentIndex % totalApartmentsPerEntrance / totalLocations
    let seekedLocationIndex = apartmentIndex % totalLocations

    let seekedEntranceNumber = seekedEntranceIndex + 1
    let seekedFloorNumber = seekedFloorIndex + 1
    let seekedLocationNumber = seekedLocationIndex + 1

    return ApartmentPlacement(
        entrance: seekedEntranceNumber,
        floor: seekedFloorNumber,
        location: seekedLocationNumber
    )
}

// The following is just tests
let values: [(ApartmentPlacement?, ApartmentPlacement?)] = [
    (calculateApartmentPlacement(for: 1, totalEntrances: 1, totalFloors: 1), ApartmentPlacement(entrance: 1, floor: 1, location: 1)),
    (calculateApartmentPlacement(for: 2, totalEntrances: 1, totalFloors: 1), ApartmentPlacement(entrance: 1, floor: 1, location: 2)),
    (calculateApartmentPlacement(for: 3, totalEntrances: 1, totalFloors: 1), ApartmentPlacement(entrance: 1, floor: 1, location: 3)),
    (calculateApartmentPlacement(for: 4, totalEntrances: 1, totalFloors: 1), ApartmentPlacement(entrance: 1, floor: 1, location: 4)),
    (calculateApartmentPlacement(for: 5, totalEntrances: 1, totalFloors: 1), nil),
    (calculateApartmentPlacement(for: 5, totalEntrances: 2, totalFloors: 1), ApartmentPlacement(entrance: 2, floor: 1, location: 1)),
    (calculateApartmentPlacement(for: 37, totalEntrances: 5, totalFloors: 3), ApartmentPlacement(entrance: 4, floor: 1, location: 1)),
    (calculateApartmentPlacement(for: 359, totalEntrances: 75, totalFloors: 12), ApartmentPlacement(entrance: 8, floor: 6, location: 3)),
]

let testValues = values.map { lhs, rhs in
    lhs == rhs
}

values.forEach { vals in
    print(vals)
}

let allTestsWorkedOut = testValues.allSatisfy { $0 }
print("All tests passed: \(allTestsWorkedOut)")