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README.md

Book Store

Welcome to Book Store on Exercism's Rust 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 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.

Source

Created by

@coriolinus

Contributed to by

@Baelyk
@cwhakes
@efx
@ErikSchierboom
@lutostag
@petertseng
@rofrol
@stringparser
@xakon
@ZapAnton

Based on

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