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Restaurant (part 10)

Java Multithreading, Level 9, Lesson 15

Under discussion

Tested on various random lists - all results as per conditions, but failed to verify,

Recursion is used when the algorithm for solving the problem is the same as the algorithm for solving part of the problem.
That's just what we have. We need to do a full search of all options and choose the best of them.

Let me remind you of the pattern used to write recursive code:
a) condition for terminating the recursion
b) condition for continuing the recursion (recursive call with a set of parameters from the previous step).
You can always find detailed information online about how to write recursion.

Our current task is to provide a recursive implementation of item 2.2 of the previous task:
(choose a list of available videos that maximizes revenues)
The recursive method must chose the set of commercials that will be displayed to the customer.

This set must meet the following requirements:
1) the amount of money received from impressions should be the maximum of all possible options
2) the total commercial playback time must NOT exceed the cooking time for the current order;
3) a video is shown no more than once for any given order;
4) if several different sets of videos will produce the same amount of money from impressions, then:
4.1) choose the option that maximizes the total time;
4.2) if the total time is the same for multiple such options, then select the option with the smallest number of videos;
5) the number of remaining impressions of any commercial in the set must be positive.

And don't forget to implement item 2.4 of the previous task (display all the relevant videos).

The revalidate() method must be called for each video shown.

Requirements:

The amount of money received from impressions should be the maximum of all possible options.
The total commercial playback time must NOT exceed the cooking time for the current order.
A video should be shown no more than once for any given order.
If there are several different sets of videos that will produce the same amount of money from impressions, then the option with the maximum total time should be selected.
If there are several different sets of videos that will produce the same amount of money and have the same total time, then the option with the minimum number of videos should be chosen.
The set should include only videos with a positive number of remaining impressions.
The revalidate() method must be called for each video shown.

package com.codegym.task.task27.task2712; import com.codegym.task.task27.task2712.kitchen.Cook; import com.codegym.task.task27.task2712.kitchen.Dish; import com.codegym.task.task27.task2712.kitchen.Waiter; import java.io.IOException; public class Restaurant { public static void main(String[] args) throws IOException { ConsoleHelper.writeMessage(Dish.allDishesToString()); Cook cook = new Cook("Amigo"); Tablet tablet = new Tablet(1); Waiter waiter = new Waiter(); tablet.addObserver(cook); cook.addObserver(waiter); tablet.createOrder(); } }

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KIN SOCHEAT

Level 34 , Phnom Penh, Cambogia

31 July 2020, 13:17

public Advertisement(Object content, String name, long amountPaid, int impressionsRemaining, int duration) { this.duration = duration; // this.amountPerImpression = (amountPaid /(long)impressionsRemaining); if (impressionsRemaining > 0) { this.amountPerImpression = (amountPaid /(long)impressionsRemaining); }

Luyi

Level 31 , Kosice, Slovakia

5 May 2020, 16:57

well, for: "If there are several different sets of videos that will produce the same amount of money from impressions, then the option with the maximum total time should be selected." put into Advertisement class into constructor: if(impressionsRemaining == 0) this.amountPerImpression = 0; else this.amountPerImpression = amountPaid/impressionsRemaining;

Abe

Level 41 , Salt Lake City, United States

23 October 2019, 18:03

One thing I had to do was in your constructor for Advertisement, if number of remaining impressions = 0, set amountPerImpression = 0. Otherwise attempting add a video with 0 remaining impressions will cause a divide by 0 exception.