import unittest
import sys
import trace
def highest_product_of_3(xs):
if len(xs) < 3:
raise Exception("List needs to contain at least three elements.")
hp3 = xs[0] * xs[1] * xs[2]
hp2 = xs[0] * xs[1]
lp2 = xs[0] * xs[1]
hn = max(xs[0], xs[1])
ln = min(xs[0], xs[1])
for x in xs[2:]:
hp3 = max(hp3, hp2 * x, lp2 * x)
hp2 = max(hp2, hn * x, ln * x)
lp2 = min(lp2, hn * x, ln * x)
hn = max(hn, x)
ln = min(ln, x)
return hp3
# Tests
class Test(unittest.TestCase):
def test_short_list(self):
actual = highest_product_of_3([1, 2, 3, 4])
expected = 24
self.assertEqual(actual, expected)
def test_longer_list(self):
actual = highest_product_of_3([6, 1, 3, 5, 7, 8, 2])
expected = 336
self.assertEqual(actual, expected)
def test_list_has_one_negative(self):
actual = highest_product_of_3([-5, 4, 8, 2, 3])
expected = 96
self.assertEqual(actual, expected)
def test_list_has_two_negatives(self):
actual = highest_product_of_3([-10, 1, 3, 2, -10])
expected = 300
self.assertEqual(actual, expected)
def test_list_is_all_negatives(self):
actual = highest_product_of_3([-5, -1, -3, -2])
expected = -6
self.assertEqual(actual, expected)
def test_error_with_empty_list(self):
with self.assertRaises(Exception):
highest_product_of_3([])
def test_error_with_one_number(self):
with self.assertRaises(Exception):
highest_product_of_3([1])
def test_error_with_two_numbers(self):
with self.assertRaises(Exception):
highest_product_of_3([1, 1])
def test_custom(self):
actual = highest_product_of_3([9, 5, 2, 1, 7, 3])
expected = 9 * 7 * 5
self.assertEqual(actual, expected)
unittest.main(verbosity=2)
def main():
highest_product_of_3([-5, -1, -3, -2])
tracer = trace.Trace(ignoredirs=[sys.prefix, sys.exec_prefix],
trace=0,
count=1)
tracer.run('main()')
r = tracer.results()
r.write_results(show_missing=True, coverdir=".")
