From 34dc3e05c8a42c47023776d52ff33f100f2d310f Mon Sep 17 00:00:00 2001 From: William Carroll Date: Sat, 18 Jan 2020 17:04:05 +0000 Subject: [PATCH] Complete practice algorithms from InterviewCake.com While I've done these algorithms before, I'm preparing for an on-site with DeepMind, so I created a subdirectory called deepmind where I'm storing my second attempts at these problems. The idea of storing them in a second directory is to remove the urge to check my existing solutions that also exist in this repository. --- deepmind/inflight-entertainment.py | 51 ++++++++++++++++++++++++++ deepmind/merging-ranges.py | 59 ++++++++++++++++++++++++++++++ deepmind/stock-price.py | 51 ++++++++++++++++++++++++++ 3 files changed, 161 insertions(+) create mode 100644 deepmind/inflight-entertainment.py create mode 100644 deepmind/merging-ranges.py create mode 100644 deepmind/stock-price.py diff --git a/deepmind/inflight-entertainment.py b/deepmind/inflight-entertainment.py new file mode 100644 index 000000000..2116b27b0 --- /dev/null +++ b/deepmind/inflight-entertainment.py @@ -0,0 +1,51 @@ +import unittest + + +def can_two_movies_fill_flight(xs, t): + seeking = set() + for x in xs: + if x in seeking: + return True + else: + seeking.add(t - x) + return False + + +# Tests + + +class Test(unittest.TestCase): + def test_short_flight(self): + result = can_two_movies_fill_flight([2, 4], 1) + self.assertFalse(result) + + def test_long_flight(self): + result = can_two_movies_fill_flight([2, 4], 6) + self.assertTrue(result) + + def test_one_movie_half_flight_length(self): + result = can_two_movies_fill_flight([3, 8], 6) + self.assertFalse(result) + + def test_two_movies_half_flight_length(self): + result = can_two_movies_fill_flight([3, 8, 3], 6) + self.assertTrue(result) + + def test_lots_of_possible_pairs(self): + result = can_two_movies_fill_flight([1, 2, 3, 4, 5, 6], 7) + self.assertTrue(result) + + def test_not_using_first_movie(self): + result = can_two_movies_fill_flight([4, 3, 2], 5) + self.assertTrue(result) + + def test_only_one_movie(self): + result = can_two_movies_fill_flight([6], 6) + self.assertFalse(result) + + def test_no_movies(self): + result = can_two_movies_fill_flight([], 2) + self.assertFalse(result) + + +unittest.main(verbosity=2) diff --git a/deepmind/merging-ranges.py b/deepmind/merging-ranges.py new file mode 100644 index 000000000..23b40793b --- /dev/null +++ b/deepmind/merging-ranges.py @@ -0,0 +1,59 @@ +import unittest + + +def merge_ranges(xs): + xs.sort() + result = [xs[0]] + for curr in xs[1:]: + a, z = result[-1] + if z >= curr[0]: + result[-1] = (a, max(z, curr[1])) + else: + result.append(curr) + return result + + +# Tests +class Test(unittest.TestCase): + def test_meetings_overlap(self): + actual = merge_ranges([(1, 3), (2, 4)]) + expected = [(1, 4)] + self.assertEqual(actual, expected) + + def test_meetings_touch(self): + actual = merge_ranges([(5, 6), (6, 8)]) + expected = [(5, 8)] + self.assertEqual(actual, expected) + + def test_meeting_contains_other_meeting(self): + actual = merge_ranges([(1, 8), (2, 5)]) + expected = [(1, 8)] + self.assertEqual(actual, expected) + + def test_meetings_stay_separate(self): + actual = merge_ranges([(1, 3), (4, 8)]) + expected = [(1, 3), (4, 8)] + self.assertEqual(actual, expected) + + def test_multiple_merged_meetings(self): + actual = merge_ranges([(1, 4), (2, 5), (5, 8)]) + expected = [(1, 8)] + self.assertEqual(actual, expected) + + def test_meetings_not_sorted(self): + actual = merge_ranges([(5, 8), (1, 4), (6, 8)]) + expected = [(1, 4), (5, 8)] + self.assertEqual(actual, expected) + + def test_one_long_meeting_contains_smaller_meetings(self): + actual = merge_ranges([(1, 10), (2, 5), (6, 8), (9, 10), (10, 12)]) + expected = [(1, 12)] + self.assertEqual(actual, expected) + + def test_sample_input(self): + actual = merge_ranges([(0, 1), (3, 5), (4, 8), (10, 12), (9, 10)]) + expected = [(0, 1), (3, 8), (9, 12)] + self.assertEqual(actual, expected) + + +unittest.main(verbosity=2) diff --git a/deepmind/stock-price.py b/deepmind/stock-price.py new file mode 100644 index 000000000..7055b66af --- /dev/null +++ b/deepmind/stock-price.py @@ -0,0 +1,51 @@ +def get_max_profit(xs): + best_profit = xs[1] - xs[0] + lowest_buy = xs[0] + + for x in xs[1:]: + best_profit = max(best_profit, x - lowest_buy) + lowest_buy = min(lowest_buy, x) + return best_profit + + +# Tests + +import unittest + + +class Test(unittest.TestCase): + def test_price_goes_up_then_down(self): + actual = get_max_profit([1, 5, 3, 2]) + expected = 4 + self.assertEqual(actual, expected) + + def test_price_goes_down_then_up(self): + actual = get_max_profit([7, 2, 8, 9]) + expected = 7 + self.assertEqual(actual, expected) + + def test_price_goes_up_all_day(self): + actual = get_max_profit([1, 6, 7, 9]) + expected = 8 + self.assertEqual(actual, expected) + + def test_price_goes_down_all_day(self): + actual = get_max_profit([9, 7, 4, 1]) + expected = -2 + self.assertEqual(actual, expected) + + def test_price_stays_the_same_all_day(self): + actual = get_max_profit([1, 1, 1, 1]) + expected = 0 + self.assertEqual(actual, expected) + + def test_error_with_empty_prices(self): + with self.assertRaises(Exception): + get_max_profit([]) + + def test_error_with_one_price(self): + with self.assertRaises(Exception): + get_max_profit([1]) + + +unittest.main(verbosity=2)