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78 lines
2.0 KiB
Python
78 lines
2.0 KiB
Python
"""Prime Check."""
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import math
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import unittest
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def prime_check(number: int) -> bool:
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"""Checks to see if a number is a prime in O(sqrt(n)).
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A number is prime if it has exactly two factors: 1 and itself.
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>>> prime_check(0)
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False
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>>> prime_check(1)
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False
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>>> prime_check(2)
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True
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>>> prime_check(3)
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True
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>>> prime_check(27)
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False
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>>> prime_check(87)
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False
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>>> prime_check(563)
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True
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>>> prime_check(2999)
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True
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>>> prime_check(67483)
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False
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"""
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if 1 < number < 4:
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# 2 and 3 are primes
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return True
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elif number < 2 or not number % 2:
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# Negatives, 0, 1 and all even numbers are not primes
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return False
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odd_numbers = range(3, int(math.sqrt(number) + 1), 2)
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return not any(not number % i for i in odd_numbers)
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class Test(unittest.TestCase):
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def test_primes(self):
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self.assertTrue(prime_check(2))
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self.assertTrue(prime_check(3))
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self.assertTrue(prime_check(5))
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self.assertTrue(prime_check(7))
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self.assertTrue(prime_check(11))
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self.assertTrue(prime_check(13))
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self.assertTrue(prime_check(17))
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self.assertTrue(prime_check(19))
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self.assertTrue(prime_check(23))
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self.assertTrue(prime_check(29))
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def test_not_primes(self):
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self.assertFalse(
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prime_check(-19),
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"Negative numbers are excluded by definition of prime numbers.",
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)
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self.assertFalse(
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prime_check(0),
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"Zero doesn't have any positive factors, primes must have exactly two.",
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)
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self.assertFalse(
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prime_check(1),
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"One only has 1 positive factor, primes must have exactly two.",
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)
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self.assertFalse(prime_check(2 * 2))
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self.assertFalse(prime_check(2 * 3))
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self.assertFalse(prime_check(3 * 3))
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self.assertFalse(prime_check(3 * 5))
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self.assertFalse(prime_check(3 * 5 * 7))
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if __name__ == "__main__":
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unittest.main()
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