From 91811236a56c6323f469d5baf6eaa4e436658bb8 Mon Sep 17 00:00:00 2001 From: William Carroll Date: Wed, 22 Jan 2020 11:06:10 +0000 Subject: [PATCH] Complete which-appears-twice Solves the InterviewCake.com problem that asks us to write a function that returns the number, y, that occurs twice in a list, xs, where xs is an unsorted list of integers from 1..n with a length of n + 1. --- deepmind/which-appears-twice.py | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) create mode 100644 deepmind/which-appears-twice.py diff --git a/deepmind/which-appears-twice.py b/deepmind/which-appears-twice.py new file mode 100644 index 000000000..c01379295 --- /dev/null +++ b/deepmind/which-appears-twice.py @@ -0,0 +1,29 @@ +import unittest + + +def find_repeat(xs): + n = max(xs) + expected_sum = (n + 1) * n / 2 + actual_sum = sum(xs) + return actual_sum - expected_sum + + +# Tests +class Test(unittest.TestCase): + def test_short_list(self): + actual = find_repeat([1, 2, 1]) + expected = 1 + self.assertEqual(actual, expected) + + def test_medium_list(self): + actual = find_repeat([4, 1, 3, 4, 2]) + expected = 4 + self.assertEqual(actual, expected) + + def test_long_list(self): + actual = find_repeat([1, 5, 9, 7, 2, 6, 3, 8, 2, 4]) + expected = 2 + self.assertEqual(actual, expected) + + +unittest.main(verbosity=2)