69 lines
2 KiB
Python
69 lines
2 KiB
Python
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import unittest
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# get_products_of_all_ints_except_at_index :: [Int] -> [Int]
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def get_products_of_all_ints_except_at_index(xs):
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n = len(xs)
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if n < 2:
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raise Exception("Cannot computer without 2 or elements")
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# lhs
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befores = [None] * n
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befores[0] = 1
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for i in range(1, n):
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befores[i] = befores[i - 1] * xs[i - 1]
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# rhs
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afters = [None] * n
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afters[-1] = 1
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for i in range(n - 2, -1, -1):
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afters[i] = afters[i + 1] * xs[i + 1]
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result = [None] * n
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for i in range(n):
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result[i] = befores[i] * afters[i]
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return result
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# Tests
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class Test(unittest.TestCase):
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def test_small_list(self):
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actual = get_products_of_all_ints_except_at_index([1, 2, 3])
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expected = [6, 3, 2]
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self.assertEqual(actual, expected)
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def test_longer_list(self):
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actual = get_products_of_all_ints_except_at_index([8, 2, 4, 3, 1, 5])
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expected = [120, 480, 240, 320, 960, 192]
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self.assertEqual(actual, expected)
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def test_list_has_one_zero(self):
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actual = get_products_of_all_ints_except_at_index([6, 2, 0, 3])
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expected = [0, 0, 36, 0]
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self.assertEqual(actual, expected)
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def test_list_has_two_zeros(self):
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actual = get_products_of_all_ints_except_at_index([4, 0, 9, 1, 0])
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expected = [0, 0, 0, 0, 0]
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self.assertEqual(actual, expected)
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def test_one_negative_number(self):
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actual = get_products_of_all_ints_except_at_index([-3, 8, 4])
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expected = [32, -12, -24]
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self.assertEqual(actual, expected)
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def test_all_negative_numbers(self):
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actual = get_products_of_all_ints_except_at_index([-7, -1, -4, -2])
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expected = [-8, -56, -14, -28]
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self.assertEqual(actual, expected)
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def test_error_with_empty_list(self):
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with self.assertRaises(Exception):
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get_products_of_all_ints_except_at_index([])
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def test_error_with_one_number(self):
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with self.assertRaises(Exception):
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get_products_of_all_ints_except_at_index([1])
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unittest.main(verbosity=2)
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