Lab #4: Snatch Solution

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Snatch!

Topic Coverage

Abstract Classes / Interfaces

Inheritance vs Composition

Design Principles

CS2030 Java Style Guide

Problem Description

Snatch is yet another transport service provider trying to vie for a place in the public transport arena.

Snatch provides three types of ride services:

JustRide

Fare is based on the distance @ 22 cents per km
Fare is the same regardless of the number of passengers (pax)

There is no booking fee.

A surcharge of 500 cents if a ride request is issued between the peak hour of 600 hrs to 900 hrs, both inclusive
TakeACab
Fare is based on the distance @ 33 cents per km, but there is a booking fee of 200 cents

Fare is the same regardless of the number of passengers (pax)

No peak hour surcharge

ShareARide
Fare is based on the distance @ 50 cents per km

Fare is divided equally among the number of passengers

There is no booking fee.

Any fractional part of the fare is absorbed by your friendly driver

A surcharge of 500 cents if a ride request is issued between 600 hrs to 900 hrs, both inclusive

In addition, there are two types of drivers under Snatch. Each can provide a subset of the services above.

NormalCab drivers provide JustRide and TakeACab services.

PrivateCar drivers provide JustRide and ShareARide services.

A customer can issue a Snatch ride request, specifed by the distance of the ride, the number of passengers, and the time of the request.

Task

You shall be given a request, followed by a list of NormalCab or PrivateCar drivers together with their corresponding waiting times. A booking is a pairing of a driver with the request. The task is to fnd the best booking with the lowest fare by matching the available drivers based on the services they provide to the given request. Break ties among the same lowest fares by selecting the booking with the smaller waiting time.

https://codecrunch.comp.nus.edu.sg/task_view.php?tid=4947
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26/11/2021, 03:16    CodeCrunch

You may assume that no two bookings have the same fare and the same waiting time.


This task is divided into several levels. Read through all the levels to see how the different levels are related.

Remember to:

always compile your program fles frst before using jshell to test your program


use checkstyle and javadoc comments to enhance code readability and facilitating code review


Level 1

Defne a Request class to handle a request comprising the distance, number of passengers, and time.


$ javac your_java_files

    • jshell -q your_java_files_in_bottom-up_dependency_order < test1.jsh jshell> new Request(20, 3, 1000)
$.. ==> 20km for 3pax @ 1000hrs jshell> new Request(10, 1, 900) $.. ==> 10km for 1pax @ 900hrs jshell> /exit

Level 2

Now include the JustRide and TakeACab services. Note that every service needs to implement the computeFare method that returns the fare in cents.


$ javac your_java_files

    • jshell -q your_java_files_in_bottom-up_dependency_order < test2.jsh jshell> new JustRide()
$.. ==> JustRide

jshell> new JustRide().computeFare(new Request(20, 3, 1000)) $.. ==> 440
jshell> new JustRide().computeFare(new Request(10, 1, 900)) $.. ==> 720
jshell> new TakeACab() $.. ==> TakeACab
jshell> new TakeACab().computeFare(new Request(20, 3, 1000)) $.. ==> 860
jshell> new TakeACab().computeFare(new Request(10, 1, 900)) $.. ==> 530
jshell> /exit

Level 3

Now, include a NormalCab driver who is identifed by its license plate number (a string) and the passenger waiting time in minutes.

Then, add a Booking class that takes in a driver and a request. From the services that a driver provides, the best service with the lowest fare is selected.

Two bookings may be compared using their computed fares; if both fares are the same, prefer the one with the shorter waiting time.


$ javac your_java_files

    • jshell -q your_java_files_in_bottom-up_dependency_order < test3.jsh jshell> new NormalCab("SHA1234", 5)
$.. ==> SHA1234 (5 mins away) NormalCab

jshell> new Booking(new NormalCab("SHA1234", 5), new Request(20, 3, 1000)) $.. ==> $4.40 using SHA1234 (5 mins away) NormalCab (JustRide)
jshell> new NormalCab("SHA2345", 10)

$.. ==> SHA2345 (10 mins away) NormalCab

jshell> new Booking(new NormalCab("SHA2345", 10), new Request(10, 1, 900)) $.. ==> $5.30 using SHA2345 (10 mins away) NormalCab (TakeACab)
jshell> Booking b1 = new Booking(new NormalCab("SHA2345", 10), new Request(10, 1, 900)) jshell> Booking b2 = new Booking(new NormalCab("SHA2345", 10), new Request(10, 1, 900)) jshell> b1.compareTo(b2) == 0
$.. ==> true

jshell> Booking b3 = new Booking(new NormalCab("SHA1234", 5), new Request(10, 1, 900)) jshell> Booking b4 = new Booking(new NormalCab("SHA2345", 10), new Request(10, 1, 900)) jshell> b3.compareTo(b4) < 0
$.. ==> true jshell> /exit

https://codecrunch.comp.nus.edu.sg/task_view.php?tid=4947
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26/11/2021, 03:16    CodeCrunch

Level 4


Now include the ShareARide service and PrivateCar driver.

You should aim to make the Booking class general such that it does not need to check for any invalid pairing, say between PrivateCar driver and TakeACab service. If you have designed your program appropriately, then extending your program with additional drivers and services would not require any modifcation to existing classes.

$ javac your_java_files

    • jshell -q your_java_files_in_bottom-up_dependency_order < test4.jsh jshell> new ShareARide()
$.. ==> ShareARide

jshell> new PrivateCar("SMA7890", 5)

$.. ==> SMA7890 (5 mins away) PrivateCar

jshell> new Booking(new PrivateCar("SMA7890", 5), new Request(20, 3, 1000)) $.. ==> $3.33 using SMA7890 (5 mins away) PrivateCar (ShareARide) jshell> new PrivateCar("SLA5678", 10)
$.. ==> SLA5678 (10 mins away) PrivateCar

jshell> new Booking(new PrivateCar("SLA5678", 10), new Request(10, 1, 900)) $.. ==> $7.20 using SLA5678 (10 mins away) PrivateCar (JustRide)
jshell> Booking b1 = new Booking(new PrivateCar("SMA7890", 5), new Request(10, 1, 900)) jshell> Booking b2 = new Booking(new PrivateCar("SLA5678", 10), new Request(10, 1, 900)) jshell> b1.compareTo(b2) < 0
$.. ==> true jshell> /exit

Level 5

Now complete the task by defning the findBestBooking method to return the best booking given a request, and an array of drivers with their waiting times. Save the method in the fle level5.jsh.

Assume that no two bookings have the same fare and the same waiting time.

$ javac your_java_files

    • jshell -q your_java_files_in_bottom-up_dependency_order level5.jsh < test5.jsh jshell> findBestBooking(new Request(20, 3, 1000),
...> new Driver[]{new NormalCab("SHA1234", 5), new PrivateCar("SMA7890", 10)}) $.. ==> $3.33 using SMA7890 (10 mins away) PrivateCar (ShareARide)
jshell> findBestBooking(new Request(10, 1, 900),

...> new Driver[]{new NormalCab("SHA1234", 5), new PrivateCar("SMA7890", 10)}) $.. ==> $5.30 using SHA1234 (5 mins away) NormalCab (TakeACab)
jshell> /exit



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