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offthecookies's solution

to Book Store in the Java Track

Published at Aug 18 2019 · 0 comments
Instructions
Test suite
Solution

To try and encourage more sales of different books from a popular 5 book series, a bookshop has decided to offer discounts on multiple book purchases.

One copy of any of the five books costs $8.

If, however, you buy two different books, you get a 5% discount on those two books.

If you buy 3 different books, you get a 10% discount.

If you buy 4 different books, you get a 20% discount.

If you buy all 5, you get a 25% discount.

Note: that if you buy four books, of which 3 are different titles, you get a 10% discount on the 3 that form part of a set, but the fourth book still costs $8.

Your mission is to write a piece of code to calculate the price of any conceivable shopping basket (containing only books of the same series), giving as big a discount as possible.

For example, how much does this basket of books cost?

  • 2 copies of the first book
  • 2 copies of the second book
  • 2 copies of the third book
  • 1 copy of the fourth book
  • 1 copy of the fifth book

One way of grouping these 8 books is:

  • 1 group of 5 --> 25% discount (1st,2nd,3rd,4th,5th)
  • +1 group of 3 --> 10% discount (1st,2nd,3rd)

This would give a total of:

  • 5 books at a 25% discount
  • +3 books at a 10% discount

Resulting in:

  • 5 x (8 - 2.00) == 5 x 6.00 == $30.00
  • +3 x (8 - 0.80) == 3 x 7.20 == $21.60

For a total of $51.60

However, a different way to group these 8 books is:

  • 1 group of 4 books --> 20% discount (1st,2nd,3rd,4th)
  • +1 group of 4 books --> 20% discount (1st,2nd,3rd,5th)

This would give a total of:

  • 4 books at a 20% discount
  • +4 books at a 20% discount

Resulting in:

  • 4 x (8 - 1.60) == 4 x 6.40 == $25.60
  • +4 x (8 - 1.60) == 4 x 6.40 == $25.60

For a total of $51.20

And $51.20 is the price with the biggest discount.

Setup

Go through the setup instructions for Java to install the necessary dependencies:

https://exercism.io/tracks/java/installation

Running the tests

You can run all the tests for an exercise by entering the following in your terminal:

$ gradle test

Use gradlew.bat if you're on Windows

In the test suites all tests but the first have been skipped.

Once you get a test passing, you can enable the next one by removing the @Ignore("Remove to run test") annotation.

Source

Inspired by the harry potter kata from Cyber-Dojo. http://cyber-dojo.org

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

BookStoreTest.java

import static org.junit.Assert.assertEquals;

import java.util.Collections;
import java.util.List;
import java.util.Arrays;

import org.junit.Before;
import org.junit.Ignore;
import org.junit.Test;

public class BookStoreTest {

    // This is sufficient accuracy since we're handling currency values, which should be equal
    // to within 2 decimal places.
    private static final double EQUALITY_TOLERANCE = 0.001;

    private BookStore bookStore;

    @Before
    public void setUp() {
        bookStore = new BookStore();
    }

    @Test
    public void onlyASingleBook() {
        List<Integer> books = Collections.singletonList(1);
        assertEquals(8.00, bookStore.calculateBasketCost(books), EQUALITY_TOLERANCE);
    }

    @Ignore("Remove to run test")
    @Test
    public void twoOfSameBook() {
        List<Integer> books = Arrays.asList(2, 2);
        assertEquals(16.00, bookStore.calculateBasketCost(books), EQUALITY_TOLERANCE);
    }

    @Ignore("Remove to run test")
    @Test
    public void emptyBasket() {
        List<Integer> books = Collections.emptyList();
        assertEquals(0.00, bookStore.calculateBasketCost(books), EQUALITY_TOLERANCE);
    }

    @Ignore("Remove to run test")
    @Test
    public void twoDifferentBooks() {
        List<Integer> books = Arrays.asList(1, 2);
        assertEquals(15.20, bookStore.calculateBasketCost(books), EQUALITY_TOLERANCE);
    }

    @Ignore("Remove to run test")
    @Test
    public void threeDifferentBooks() {
        List<Integer> books = Arrays.asList(1, 2, 3);
        assertEquals(21.60, bookStore.calculateBasketCost(books), EQUALITY_TOLERANCE);
    }

    @Ignore("Remove to run test")
    @Test
    public void fourDifferentBooks() {
        List<Integer> books = Arrays.asList(1, 2, 3, 4);
        assertEquals(25.60, bookStore.calculateBasketCost(books), EQUALITY_TOLERANCE);
    }

    @Ignore("Remove to run test")
    @Test
    public void fiveDifferentBooks() {
        List<Integer> books = Arrays.asList(1, 2, 3, 4, 5);
        assertEquals(30.00, bookStore.calculateBasketCost(books), EQUALITY_TOLERANCE);
    }

    @Ignore("Remove to run test")
    @Test
    public void twoGroupsOfFourIsCheaperThanGroupOfFivePlusGroupOfThree() {
        List<Integer> books = Arrays.asList(1, 1, 2, 2, 3, 3, 4, 5);
        assertEquals(51.20, bookStore.calculateBasketCost(books), EQUALITY_TOLERANCE);
    }

    @Ignore("Remove to run test")
    @Test
    public void twoGroupsOfFourIsCheaperThanGroupsOfFiveAndThree() {
        List<Integer> books = Arrays.asList(1, 1, 2, 3, 4, 4, 5, 5);
        assertEquals(51.20, bookStore.calculateBasketCost(books), EQUALITY_TOLERANCE);
    }

    @Ignore("Remove to run test")
    @Test
    public void groupOfFourPlusGroupOfTwoIsCheaperThanTwoGroupsOfThree() {
        List<Integer> books = Arrays.asList(1, 1, 2, 2, 3, 4);
        assertEquals(40.80, bookStore.calculateBasketCost(books), EQUALITY_TOLERANCE);
    }

    @Ignore("Remove to run test")
    @Test
    public void twoEachOfFirst4BooksAnd1CopyEachOfRest() {
        List<Integer> books = Arrays.asList(1, 1, 2, 2, 3, 3, 4, 4, 5);
        assertEquals(55.60, bookStore.calculateBasketCost(books), EQUALITY_TOLERANCE);
    }

    @Ignore("Remove to run test")
    @Test
    public void twoCopiesOfEachBook() {
        List<Integer> books = Arrays.asList(1, 1, 2, 2, 3, 3, 4, 4, 5, 5);
        assertEquals(60.00, bookStore.calculateBasketCost(books), EQUALITY_TOLERANCE);
    }

    @Ignore("Remove to run test")
    @Test
    public void threeCopiesOfFirstBookAnd2EachOfRemaining() {
        List<Integer> books = Arrays.asList(1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 1);
        assertEquals(68.00, bookStore.calculateBasketCost(books), EQUALITY_TOLERANCE);
    }

    @Ignore("Remove to run test")
    @Test
    public void threeEachOFirst2BooksAnd2EachOfRemainingBooks() {
        List<Integer> books = Arrays.asList(1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 1, 2);
        assertEquals(75.20, bookStore.calculateBasketCost(books), EQUALITY_TOLERANCE);
    }

    @Ignore("Remove to run test")
    @Test
    public void fourGroupsOfFourAreCheaperThanTwoGroupsEachOfFiveAndThree() {
        List<Integer> books = Arrays.asList(1, 1, 2, 2, 3, 3, 4, 5, 1, 1, 2, 2, 3, 3, 4, 5);
        assertEquals(102.4, bookStore.calculateBasketCost(books), EQUALITY_TOLERANCE);
    }
}

src/test/java/Bookstore.java

// books will be instantiated into this class as objects
// calculations will be made in this class




import java.util.ArrayList;

class Bookstore {

	// instance variables
	String bookList;
	String book1, book2, book3, book4, book5;

	// int instance variable that counts the amount of books
	// use this to fifure out which discount to give
	int count,amount;

	// constructor
	Bookstore(String bookList) {
		this.bookList = bookList;

	}

	// split the String book list into each seperate book
	void eachBook(String myList) {
		System.out.println(bookList);
		String[] myBooks = bookList.split(", ");

		// count amount of books here, then use that in the discount
		// need to check if any books are the same
		count = myBooks.length;

		if (count!=5) {
			System.exit(0);
		}		

		// check what myBooks looks like after split
		// to tell if any books are the same, create an if statement
		// if myBook[0]=myBook[1] and so on, so forth
		book1 = myBooks[0];
		book2 = myBooks[1];
		book3 = myBooks[2];
		book4 = myBooks[3];
		book5 = myBooks[4];

		// check if any books are same here
		if (book1.equals(book2)) {count=count-1;}
		else if (book1.equals(book3)) {count=count-1;}
		else if (book1.equals(book4)) {count=count-1;}
		else if (book1.equals(book5)) {count=count-1;}

		if (book2.equals(book3)) {count=count-1;}
		else if (book2.equals(book4)) {count=count-1;}
		else if (book2.equals(book5)) {count=count-1;}

		if (book3.equals(book4)) {count=count-1;}
		else if (book3.equals(book5)) {count=count-1;}

		if (book4.equals(book5)) {count=count-1;}

		amount=count;

	}

	// use this method to give discount
	// use count the amount of books to decide on what discount to give
	public double discount(double total) {

		double sameBook=0;

		if (amount>count) {
			if (amount==count+1) {
				sameBook=8;
				count=count-1;
				System.out.println("check");	
			}
			else if (amount==count+2) {
				sameBook=16;
				count=count-2;
			}
			else if (amount==count+3) {
				sameBook=24;
				count=count-3;
			}
			else if (amount==count+4) {
				sameBook=32;
				count=count-4;
			}

		}
	
		if (count == 1.0) {
			total = 8 + sameBook;
			return total;			
		}
		else if (count == 2) {
			total = 16 * .95 + sameBook;
			return total;
		}
		else if (count == 3) {
			total = 24 * .9 + sameBook;
			return total;
		}
		else if (count == 4) {
			total = 32 * .8 + sameBook;
			return total;
		}
		else {
			total = 40 * .75 + sameBook;
			return total;
		}

		
	}



	// need a toString method
	public String toString() {
		return bookList;
	}


}

src/test/java/main.java

// use this class to call the objects
import java.util.Scanner;

// program isn't complete but don't feel like working on it anymore


class main {

	public static void main(String[] args) {

		Scanner myScanner = new Scanner(System.in);

		// while statement the user will
		// contiue to add books to the list until they hit q or
		// the list maxes out at 5 books
		// write this program, then try to figure out how to give
		// discount if books are not from the same series
		// see instructions



		System.out.println("What book would you like to purchase?");
		String book = myScanner.next();
		double count=0;

		String allBooks = book + ", ";

		// why does this not work, if nothing else could put a while 
		// statement withan another while statement
		while (count!=5 && !book.equals("q")) {
			System.out.println("What book would you like to purchase?");
			book = myScanner.next();

			// if statement to end while statement when q is entered
			if (book.equals("q")) {
				break;
			}
			allBooks = allBooks + book + ", ";
			count=count+1;
		}

		Bookstore myBook = new Bookstore(allBooks);
		
		myBook.eachBook(allBooks);

		System.out.println(myBook.discount(count));


		myScanner.close();

	}




}

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