add bookstore problem (#92)

* add bookstore problem

* fix bookstore stub file, better readability on solution

* book-store difficulty 3->5

Author: hucancode

config.json

@@ -179,6 +179,14 @@
         "prerequisites": [],
         "difficulty": 5
       },
+      {
+        "slug": "book-store",
+        "name": "Book Store",
+        "uuid": "590c6355-dbb4-44a0-a2d7-98490055c7e9",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 5
+      },
       {
         "slug": "change",
         "name": "Change",

exercises/practice/book-store/.docs/instructions.md

@@ -0,0 +1,61 @@
+# 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 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 (1st, 2nd,3rd, 4th, 5th)
+- 1 group of 3 (1st, 2nd, 3rd)
+
+This would give a total of:
+
+- 5 books at a 25% discount
+- 3 books at a 10% discount
+
+Resulting in:
+
+- 5 × (100% - 25%) × $8 = 5 × $6.00 = $30.00, plus
+- 3 × (100% - 10%) × $8 = 3 × $7.20 = $21.60
+
+Which equals $51.60.
+
+However, a different way to group these 8 books is:
+
+- 1 group of 4 books (1st, 2nd, 3rd, 4th)
+- 1 group of 4 books (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 × (100% - 20%) × $8 = 4 × $6.40 = $25.60, plus
+- 4 × (100% - 20%) × $8 = 4 × $6.40 = $25.60
+
+Which equals $51.20.
+
+And $51.20 is the price with the biggest discount.

exercises/practice/book-store/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "hucancode"
+  ],
+  "files": {
+    "solution": [
+      "book_store.odin"
+    ],
+    "test": [
+      "book_store_test.odin"
+    ],
+    "example": [
+      ".meta/example.odin"
+    ]
+  },
+  "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": "https://cyber-dojo.org"
+}

exercises/practice/book-store/.meta/example.odin

@@ -0,0 +1,44 @@
+package book_store
+
+import "core:slice"
+
+calculate :: proc(counts: []u32) -> u32 {
+	grand_total: f32 = 0.0
+	used: u32 = 0
+	BASE_PRICE: f32 : 800.0
+	n := len(counts)
+	get_discount :: proc(book: int) -> f32 {
+		switch book {
+		case 2:
+			return 0.95
+		case 3:
+			return 0.90
+		case 4:
+			return 0.80
+		case 5:
+			return 0.75
+		case:
+			return 1.0
+		}
+	}
+	for i in 0 ..< n {
+		m := n - i
+		x := counts[i] - used
+		used = counts[i]
+		price := BASE_PRICE * f32(m) * f32(x)
+		grand_total += price * get_discount(m)
+	}
+	return u32(grand_total)
+}
+
+total :: proc(basket: []u32) -> u32 {
+	counts: [5]u32
+	for book in basket {
+		counts[book - 1] += 1
+	}
+	slice.sort(counts[:])
+	delta := min(counts[0], counts[2] - counts[1])
+	counts[0] -= delta
+	counts[1] += delta
+	return calculate(counts[:])
+}

exercises/practice/book-store/.meta/tests.toml

@@ -0,0 +1,64 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[17146bd5-2e80-4557-ab4c-05632b6b0d01]
+description = "Only a single book"
+
+[cc2de9ac-ff2a-4efd-b7c7-bfe0f43271ce]
+description = "Two of the same book"
+
+[5a86eac0-45d2-46aa-bbf0-266b94393a1a]
+description = "Empty basket"
+
+[158bd19a-3db4-4468-ae85-e0638a688990]
+description = "Two different books"
+
+[f3833f6b-9332-4a1f-ad98-6c3f8e30e163]
+description = "Three different books"
+
+[1951a1db-2fb6-4cd1-a69a-f691b6dd30a2]
+description = "Four different books"
+
+[d70f6682-3019-4c3f-aede-83c6a8c647a3]
+description = "Five different books"
+
+[78cacb57-911a-45f1-be52-2a5bd428c634]
+description = "Two groups of four is cheaper than group of five plus group of three"
+
+[f808b5a4-e01f-4c0d-881f-f7b90d9739da]
+description = "Two groups of four is cheaper than groups of five and three"
+
+[fe96401c-5268-4be2-9d9e-19b76478007c]
+description = "Group of four plus group of two is cheaper than two groups of three"
+
+[68ea9b78-10ad-420e-a766-836a501d3633]
+description = "Two each of first four books and one copy each of rest"
+
+[c0a779d5-a40c-47ae-9828-a340e936b866]
+description = "Two copies of each book"
+
+[18fd86fe-08f1-4b68-969b-392b8af20513]
+description = "Three copies of first book and two each of remaining"
+
+[0b19a24d-e4cf-4ec8-9db2-8899a41af0da]
+description = "Three each of first two books and two each of remaining books"
+
+[bb376344-4fb2-49ab-ab85-e38d8354a58d]
+description = "Four groups of four are cheaper than two groups each of five and three"
+
+[5260ddde-2703-4915-b45a-e54dbbac4303]
+description = "Check that groups of four are created properly even when there are more groups of three than groups of five"
+
+[b0478278-c551-4747-b0fc-7e0be3158b1f]
+description = "One group of one and four is cheaper than one group of two and three"
+
+[cf868453-6484-4ae1-9dfc-f8ee85bbde01]
+description = "One group of one and two plus three groups of four is cheaper than one group of each size"

exercises/practice/book-store/book_store.odin

@@ -0,0 +1,6 @@
+package book_store
+
+total :: proc(books: []u32) -> u32 {
+	// Implement this procedure.
+	return 0
+}

exercises/practice/book-store/book_store_test.odin

@@ -0,0 +1,153 @@
+package book_store
+
+import "core:testing"
+
+@(test)
+test_only_a_single_book :: proc(t: ^testing.T) {
+	basket := [?]u32{1}
+	result := total(basket[:])
+	expected: u32 = 800
+	testing.expect_value(t, result, expected)
+}
+
+@(test)
+test_two_of_the_same_book :: proc(t: ^testing.T) {
+	basket := [?]u32{2, 2}
+	result := total(basket[:])
+	expected: u32 = 1600
+	testing.expect_value(t, result, expected)
+}
+
+@(test)
+test_empty_basket :: proc(t: ^testing.T) {
+	basket := [?]u32{}
+	result := total(basket[:])
+	expected: u32 = 0
+	testing.expect_value(t, result, expected)
+}
+
+@(test)
+test_two_different_books :: proc(t: ^testing.T) {
+	basket := [?]u32{1, 2}
+	result := total(basket[:])
+	expected: u32 = 1520
+	testing.expect_value(t, result, expected)
+}
+
+@(test)
+test_three_different_books :: proc(t: ^testing.T) {
+	basket := [?]u32{1, 2, 3}
+	result := total(basket[:])
+	expected: u32 = 2160
+	testing.expect_value(t, result, expected)
+}
+
+@(test)
+test_four_different_books :: proc(t: ^testing.T) {
+	basket := [?]u32{1, 2, 3, 4}
+	result := total(basket[:])
+	expected: u32 = 2560
+	testing.expect_value(t, result, expected)
+}
+
+@(test)
+test_five_different_books :: proc(t: ^testing.T) {
+	basket := [?]u32{1, 2, 3, 4, 5}
+	result := total(basket[:])
+	expected: u32 = 3000
+	testing.expect_value(t, result, expected)
+}
+
+@(test)
+test_two_groups_of_four_is_cheaper_than_group_of_five_plus_group_of_three :: proc(t: ^testing.T) {
+	basket := [?]u32{1, 1, 2, 2, 3, 3, 4, 5}
+	result := total(basket[:])
+	expected: u32 = 5120
+	testing.expect_value(t, result, expected)
+}
+
+@(test)
+test_two_groups_of_four_is_cheaper_than_groups_of_five_and_three :: proc(t: ^testing.T) {
+	basket := [?]u32{1, 1, 2, 3, 4, 4, 5, 5}
+	result := total(basket[:])
+	expected: u32 = 5120
+	testing.expect_value(t, result, expected)
+}
+
+@(test)
+test_group_of_four_plus_group_of_two_is_cheaper_than_two_groups_of_three :: proc(t: ^testing.T) {
+	basket := [?]u32{1, 1, 2, 2, 3, 4}
+	result := total(basket[:])
+	expected: u32 = 4080
+	testing.expect_value(t, result, expected)
+}
+
+@(test)
+test_two_each_of_first_four_books_and_one_copy_each_of_rest :: proc(t: ^testing.T) {
+	basket := [?]u32{1, 1, 2, 2, 3, 3, 4, 4, 5}
+	result := total(basket[:])
+	expected: u32 = 5560
+	testing.expect_value(t, result, expected)
+}
+
+@(test)
+test_two_copies_of_each_book :: proc(t: ^testing.T) {
+	basket := [?]u32{1, 1, 2, 2, 3, 3, 4, 4, 5, 5}
+	result := total(basket[:])
+	expected: u32 = 6000
+	testing.expect_value(t, result, expected)
+}
+
+@(test)
+test_three_copies_of_first_book_and_two_each_of_remaining :: proc(t: ^testing.T) {
+	basket := [?]u32{1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 1}
+	result := total(basket[:])
+	expected: u32 = 6800
+	testing.expect_value(t, result, expected)
+}
+
+@(test)
+test_three_each_of_first_two_books_and_two_each_of_remaining_books :: proc(t: ^testing.T) {
+	basket := [?]u32{1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 1, 2}
+	result := total(basket[:])
+	expected: u32 = 7520
+	testing.expect_value(t, result, expected)
+}
+
+@(test)
+test_four_groups_of_four_are_cheaper_than_two_groups_each_of_five_and_three :: proc(
+	t: ^testing.T,
+) {
+	basket := [?]u32{1, 1, 2, 2, 3, 3, 4, 5, 1, 1, 2, 2, 3, 3, 4, 5}
+	result := total(basket[:])
+	expected: u32 = 10240
+	testing.expect_value(t, result, expected)
+}
+
+@(test)
+test_check_that_groups_of_four_are_created_properly_even_when_there_are_more_groups_of_three_than_groups_of_five :: proc(
+	t: ^testing.T,
+) {
+	basket := [?]u32{1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 5, 5}
+	result := total(basket[:])
+	expected: u32 = 14560
+	testing.expect_value(t, result, expected)
+}
+
+@(test)
+test_one_group_of_one_and_four_is_cheaper_than_one_group_of_two_and_three :: proc(t: ^testing.T) {
+	basket := [?]u32{1, 1, 2, 3, 4}
+	result := total(basket[:])
+	expected: u32 = 3360
+	testing.expect_value(t, result, expected)
+}
+
+@(test)
+test_one_group_of_one_and_two_plus_three_groups_of_four_is_cheaper_than_one_group_of_each_size :: proc(
+	t: ^testing.T,
+) {
+	basket := [?]u32{1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5}
+	result := total(basket[:])
+	expected: u32 = 10000
+	testing.expect_value(t, result, expected)
+}