Book Store

Welcome to Book Store on Exercism's Go Track. If you need help running the tests or submitting your code, check out HELP.md.

Instructions

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 * (8 - 2.00) == 5 * 6.00 == $30.00
+3 * (8 - 0.80) == 3 * 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 * (8 - 1.60) == 4 * 6.40 == $25.60
+4 * (8 - 1.60) == 4 * 6.40 == $25.60

For a total of $51.20

And $51.20 is the price with the biggest discount.

Define a single Go func, Cost, which calculates the cost for a given list of books based on the defined discounts.

Use the following signature for func Cost:

func Cost(books []int) int

Cost will return the total cost (after discounts) in cents. For example, for a single book, the cost is 800 cents, which equals $8.00. Only integer calculations are necessary for this exercise.

Source

Created by

@magic003

Contributed to by

@bitfield
@ekingery
@ferhatelmas
@hilary
@ilmanzo
@leenipper
@sebito91

Based on