import unittest
# get_products_of_all_ints_except_at_index :: [Int] -> [Int]
def get_products_of_all_ints_except_at_index(xs):
n = len(xs)
if n < 2:
raise Exception("Cannot computer without 2 or elements")
# lhs
befores = [None] * n
befores[0] = 1
for i in range(1, n):
befores[i] = befores[i - 1] * xs[i - 1]
# rhs
afters = [None] * n
afters[-1] = 1
for i in range(n - 2, -1, -1):
afters[i] = afters[i + 1] * xs[i + 1]
result = [None] * n
for i in range(n):
result[i] = befores[i] * afters[i]
return result
# 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)
