1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
|
import unittest
def get_max_profit(xs):
if len(xs) < 2:
raise Exception('Can only trade with two or more ticker values.')
lowest_buy = xs[0]
max_profit = None
for x in xs[1:]:
if not max_profit:
max_profit = x - lowest_buy
else:
max_profit = max(max_profit, x - lowest_buy)
lowest_buy = min(lowest_buy, x)
return max_profit
# Tests
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)
|
