# Book Store in Rust

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

1 | ```
exercism fetch rust book-store
``` |

# Book Store

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.

## Rust Installation

Refer to the exercism help page for Rust installation and learning resources.

## Writing the Code

Execute the tests with:

1 |
```
$ cargo test
``` |

All but the first test have been ignored. After you get the first test to
pass, remove the ignore flag (`#[ignore]`

) from the next test and get the tests
to pass again. The test file is located in the `tests`

directory. You can
also remove the ignore flag from all the tests to get them to run all at once
if you wish.

Make sure to read the Modules chapter if you haven't already, it will help you with organizing your files.

## Feedback, Issues, Pull Requests

The exercism/rust repository on GitHub is the home for all of the Rust exercises. If you have feedback about an exercise, or want to help implement new exercises, head over there and create an issue. Members of the rust track team are happy to help!

If you want to know more about Exercism, take a look at the contribution guide.

## 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.