From d4d8397e5ffe6734ed5861e48ce475848956a3fe Mon Sep 17 00:00:00 2001 From: William Carroll Date: Wed, 15 Jan 2020 14:25:33 +0000 Subject: Add InterviewCake.com examples Adds some of the code I generated while studying for a role transfer at Google using the fantastic resource, InterviewCake.com. This work predates the mono-repo. I should think of ways to DRY up this code and the code in crack_the_coding_interview, but I'm afraid I'm creating unnecessary work for myself that way. --- .../product-of-other-numbers.py | 68 ++++++++++++++++++++++ 1 file changed, 68 insertions(+) create mode 100644 data_structures_and_algorithms/product-of-other-numbers.py (limited to 'data_structures_and_algorithms/product-of-other-numbers.py') diff --git a/data_structures_and_algorithms/product-of-other-numbers.py b/data_structures_and_algorithms/product-of-other-numbers.py new file mode 100644 index 000000000000..d05e82d42b02 --- /dev/null +++ b/data_structures_and_algorithms/product-of-other-numbers.py @@ -0,0 +1,68 @@ +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) -- cgit 1.4.1