Book Store in Go
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.
exercism fetch go 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
- 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
- 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.
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.
Running the tests
To run the tests run the command
go test from within the exercise directory.
If the test suite contains benchmarks, you can run these with the
go test -bench .
Keep in mind that each reviewer will run benchmarks on a different machine, with different specs, so the results from these benchmark tests may vary.
For more detailed information about the Go track, including how to get help if you're having trouble, please visit the exercism.io Go language page.
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.