55 lines
1.5 KiB
Python
55 lines
1.5 KiB
Python
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import unittest
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def get_max_profit(xs):
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if len(xs) < 2:
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raise Exception('Can only trade with two or more ticker values.')
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lowest_buy = xs[0]
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max_profit = None
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for x in xs[1:]:
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if not max_profit:
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max_profit = x - lowest_buy
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else:
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max_profit = max(max_profit, x - lowest_buy)
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lowest_buy = min(lowest_buy, x)
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return max_profit
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# Tests
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class Test(unittest.TestCase):
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def test_price_goes_up_then_down(self):
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actual = get_max_profit([1, 5, 3, 2])
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expected = 4
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self.assertEqual(actual, expected)
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def test_price_goes_down_then_up(self):
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actual = get_max_profit([7, 2, 8, 9])
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expected = 7
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self.assertEqual(actual, expected)
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def test_price_goes_up_all_day(self):
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actual = get_max_profit([1, 6, 7, 9])
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expected = 8
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self.assertEqual(actual, expected)
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def test_price_goes_down_all_day(self):
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actual = get_max_profit([9, 7, 4, 1])
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expected = -2
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self.assertEqual(actual, expected)
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def test_price_stays_the_same_all_day(self):
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actual = get_max_profit([1, 1, 1, 1])
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expected = 0
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self.assertEqual(actual, expected)
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def test_error_with_empty_prices(self):
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with self.assertRaises(Exception):
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get_max_profit([])
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def test_error_with_one_price(self):
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with self.assertRaises(Exception):
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get_max_profit([1])
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unittest.main(verbosity=2)
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