New Exercise book-store

exercises/book-store/canonical-data.json

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+{
+   "book-store": {
+      "description": "Calculate lowest price for shopping basket only containing books from a single series",
+      "cases": [
+         {
+            "description": "TestSingleBookPrice",
+            "expected": 8.0
+         },
+         {
+            "description": "TestBasketContainsMyBooks",
+		    "mybasket": "3"
+            "expected": "3"
+         },
+         {
+            "description": "TestTotalBasketPriceSingleBook",
+            "basket": "1",
+            "expected": 8.0
+         },
+         {
+            "description": "TestTotalBasketPriceTwoofSameBook",
+            "basket": "22",
+            "expected": 16.0
+         },
+         {
+            "description": "TestTotalBasketPriceEmptyBasket",
+            "basket": "",
+            "expected": 0.0
+         },
+         {
+            "description": "TestBasketWith2DifferentBooks",
+            "basket": "12",
+            "expected": 15.2
+         },
+         {
+            "description": "TestBasketWith3DifferentBooks",
+            "basket": "123",
+            "expected": 21.60
+         },
+         {
+            "description": "TestBasketWith4DifferentBooks",
+            "basket": "1234",
+            "expected": 25.60
+         },
+         {
+            "description": "TestBasketWith5DifferentBooks",
+            "basket": "12345",
+            "expected": 30.00
+         },
+         {
+            "description": "basket 11223345",
+            "basket": "11223345",
+            "expected": 51.20
+         },
+         {
+            "description": "basket 112233445",
+            "basket": "112233445",
+            "expected": 55.60
+         },
+         {
+            "description": "basket 1122334455",
+            "basket":  "1122334455",
+            "expected": 60.00
+         },
+         {
+            "description": "basket 11223344551",
+            "basket": "11223344551",
+            "expected": 68.00
+         },
+         {
+            "description": "basket 112233445512",
+            "basket": "112233445512",
+            "expected": 75.20
+         }
+   ]
+}
+}

exercises/book-store/description.md

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+To try and encourage more sales of the 5 different books they sell in a popular series, a bookshop has decided to offer 
+discounts of multiple-book purchases. 
+
+One copy of any of the five books costs 8 EUR. 
+
+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 go the whole hog, and buy all 5, you get a huge 25% discount. 
+
+Note that if you buy, say, 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 EUR. 
+
+Your mission is to write a piece of code to calculate the price of any conceivable shopping basket (containing only books from 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 group 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
+Giving
+ 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
+Giving
+ 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.

exercises/book-store/metadata.yml

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+---
+blurb: "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."
+source: "Inspired by the harry potter kata from Cyber-Dojo."
+source_url: "http://cyber-dojo.org"