import unittest
################################################################################
# Solution
################################################################################
# f :: [Int] -> [Int]
def get_products_of_all_ints_except_at_index(xs):
if len(xs) in {0, 1}:
raise Exception
ct = len(xs)
lefts = [1] * ct
rights = [1] * ct
result = []
for i in range(1, ct):
lefts[i] = lefts[i - 1] * xs[i - 1]
for i in range(ct - 2, -1, -1):
rights[i] = rights[i + 1] * xs[i + 1]
return [lefts[i] * rights[i] for i in range(ct)]
################################################################################
# Tests
################################################################################
class Test(unittest.TestCase):
def test_small_list(self):
actual = get_products_of_all_ints_except_at_index([1, 2, 3])
expected = [6, 3, 2]
self.assertEqual(actual, expected)
def test_longer_list(self):
actual = get_products_of_all_ints_except_at_index([8, 2, 4, 3, 1, 5])
expected = [120, 480, 240, 320, 960, 192]
self.assertEqual(actual, expected)
def test_list_has_one_zero(self):
actual = get_products_of_all_ints_except_at_index([6, 2, 0, 3])
expected = [0, 0, 36, 0]
self.assertEqual(actual, expected)
def test_list_has_two_zeros(self):
actual = get_products_of_all_ints_except_at_index([4, 0, 9, 1, 0])
expected = [0, 0, 0, 0, 0]
self.assertEqual(actual, expected)
def test_one_negative_number(self):
actual = get_products_of_all_ints_except_at_index([-3, 8, 4])
expected = [32, -12, -24]
self.assertEqual(actual, expected)
def test_all_negative_numbers(self):
actual = get_products_of_all_ints_except_at_index([-7, -1, -4, -2])
expected = [-8, -56, -14, -28]
self.assertEqual(actual, expected)
def test_error_with_empty_list(self):
with self.assertRaises(Exception):
get_products_of_all_ints_except_at_index([])
def test_error_with_one_number(self):
with self.assertRaises(Exception):
get_products_of_all_ints_except_at_index([1])
unittest.main(verbosity=2)
