Coding skills. ParkingBill.swift

import Foundation
import Glibc

// Solution @ Sergey Leschev, Belarusian State University

// Coding skills. ParkingBill.

// You parked your car in a parking lot and want to compute the total cost of the ticket. The billing rules are as follows:
// The entrance fee of the car parking lot is 2;
// The first full or partial hour costs 3;
// Each successive full or partial hour (after the first) costs 4.
// You entered the car parking lot at time E and left at time L. In this task, times are represented as strings in the format "HH:MM" (where "HH" is a two-digit number between 0 and 23, which stands for hours, and "MM" is a two-digit number between 0 and 59, which stands for minutes).

// Write a function:
// class Solution { public int solution(String E, String L); }
// that, given strings E and L specifying points in time in the format "HH:MM", returns the total cost of the parking bill from your entry at time E to your exit at time L. You can assume that E describes a time before L on the same day.

// For example, given "10:00" and "13:21" your function should return 17, because the entrance fee equals 2, the first hour costs 3 and there are two more full hours and part of a further hour, so the total cost is 2 + 3 + (3 * 4) = 17. Given "09:42" and "11:42" your function should return 9, because the entrance fee equals 2, the first hour costs 3 and the second hour costs 4, so the total cost is 2 + 3 + 4 = 9.

// Assume that:
// strings E and L follow the format "HH:MM" strictly;
// string E describes a time before L on the same day.
// In your solution, focus on correctness. The performance of your solution will not be the focus of the assessment.

public func solution(_ E: inout String, _ L: inout String) -> Int {
    var cost = 2 + 3    
    var duration = timestamp(L) - timestamp(E)


    func timestamp(_ input: String) -> Int {
        let components = input.components(separatedBy: ":").compactMap { Int($0) }
        return components[0] * 60 + components[1]
    }

    duration -= 60
    if duration > 0 { cost += Int((Double(duration) / 60.0).rounded(.up)) * 4 }
    return cost
}