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book-store: Add new exercise (exercism#465)
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‎config.json‎

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"topics": [
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]
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},
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{
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"slug": "book-store",
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"difficulty": 1,
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"topics": [
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]
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},
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{
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"slug": "linked-list",
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"difficulty": 1,

‎exercises/book-store/book_store.py‎

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def calculate_total():
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pass

‎exercises/book-store/book_store_test.py‎

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import unittest
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from book_store import calculate_total
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# test cases adapted from `x-common//canonical-data.json` @ version: 1.0.0
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class BookStoreTests(unittest.TestCase):
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def test_only_a_single_book(self):
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self.assertAlmostEqual(calculate_total([1]), 8.00,
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places=2)
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def test_two_of_the_same_book(self):
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self.assertAlmostEqual(calculate_total([2, 2]), 16.00,
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places=2)
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def test_empty_basket(self):
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self.assertAlmostEqual(calculate_total([]), 0.00,
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places=2)
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def test_two_different_books(self):
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self.assertAlmostEqual(calculate_total([1, 2]), 15.20,
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places=2)
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def test_three_different_books(self):
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self.assertAlmostEqual(calculate_total([1, 2, 3]), 21.60,
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places=2)
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def test_four_different_books(self):
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self.assertAlmostEqual(calculate_total([1, 2, 3, 4]), 25.60,
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places=2)
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def test_five_different_books(self):
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self.assertAlmostEqual(
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calculate_total([1, 2, 3, 4, 5]), 30.00,
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places=2)
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def test_two_groups_of_4_is_cheaper_than_group_of_5_plus_group_of_3(self):
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self.assertAlmostEqual(
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calculate_total([1, 1, 2, 2, 3, 3, 4, 5]), 51.20,
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places=2)
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def test_group_of_4_plus_group_of_2_is_cheaper_than_2_groups_of_3(self):
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self.assertAlmostEqual(
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calculate_total([1, 1, 2, 2, 3, 4]), 40.80,
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places=2)
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def test_two_each_of_first_4_books_and_1_copy_each_of_rest(self):
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self.assertAlmostEqual(
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calculate_total([1, 1, 2, 2, 3, 3, 4, 4, 5]), 55.60,
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places=2)
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def test_two_copies_of_each_book(self):
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self.assertAlmostEqual(
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calculate_total([1, 1, 2, 2, 3, 3, 4, 4, 5, 5]), 60.00,
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places=2)
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def test_three_copies_of_first_book_and_2_each_of_remaining(self):
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self.assertAlmostEqual(
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calculate_total([1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 1]),
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68.00,
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places=2)
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def test_three_each_of_first_2_books_and_2_each_of_remaining_books(self):
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self.assertAlmostEqual(
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calculate_total([1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 1, 2]),
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75.20,
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places=2)
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if __name__ == '__main__':
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unittest.main()

‎exercises/book-store/example.py‎

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BOOK_PRICE = 8
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def _group_price(size):
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discounts = [0, .05, .1, .2, .25]
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if not (0 < size <= 5):
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raise ValueError('size must be in 1..' + len(discounts))
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return 8 * size * (1 - discounts[size - 1])
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def calculate_total(books, price_so_far=0.):
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if not books:
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return price_so_far
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groups = list(set(books))
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min_price = float('inf')
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for i in range(len(groups)):
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remaining_books = books[:]
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for v in groups[:i + 1]:
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remaining_books.remove(v)
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price = calculate_total(remaining_books,
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price_so_far + _group_price(i + 1))
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min_price = min(min_price, price)
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return min_price

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