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871f8f4e00
* More efficient least common multiple. * lowest -> least * integer division * Update least_common_multiple.py Co-authored-by: Christian Clauss <cclauss@me.com>
96 lines
2.6 KiB
Python
96 lines
2.6 KiB
Python
import unittest
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from timeit import timeit
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def least_common_multiple_slow(first_num: int, second_num: int) -> int:
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"""
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Find the least common multiple of two numbers.
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Learn more: https://en.wikipedia.org/wiki/Least_common_multiple
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>>> least_common_multiple_slow(5, 2)
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10
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>>> least_common_multiple_slow(12, 76)
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228
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"""
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max_num = first_num if first_num >= second_num else second_num
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common_mult = max_num
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while (common_mult % first_num > 0) or (common_mult % second_num > 0):
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common_mult += max_num
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return common_mult
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def greatest_common_divisor(a: int, b: int) -> int:
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"""
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Calculate Greatest Common Divisor (GCD).
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see greatest_common_divisor.py
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>>> greatest_common_divisor(24, 40)
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8
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>>> greatest_common_divisor(1, 1)
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1
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>>> greatest_common_divisor(1, 800)
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1
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>>> greatest_common_divisor(11, 37)
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1
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>>> greatest_common_divisor(3, 5)
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1
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>>> greatest_common_divisor(16, 4)
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4
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"""
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return b if a == 0 else greatest_common_divisor(b % a, a)
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def least_common_multiple_fast(first_num: int, second_num: int) -> int:
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"""
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Find the least common multiple of two numbers.
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https://en.wikipedia.org/wiki/Least_common_multiple#Using_the_greatest_common_divisor
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>>> least_common_multiple_fast(5,2)
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10
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>>> least_common_multiple_fast(12,76)
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228
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"""
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return first_num // greatest_common_divisor(first_num, second_num) * second_num
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def benchmark():
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setup = (
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"from __main__ import least_common_multiple_slow, least_common_multiple_fast"
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)
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print(
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"least_common_multiple_slow():",
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timeit("least_common_multiple_slow(1000, 999)", setup=setup),
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)
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print(
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"least_common_multiple_fast():",
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timeit("least_common_multiple_fast(1000, 999)", setup=setup),
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)
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class TestLeastCommonMultiple(unittest.TestCase):
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test_inputs = [
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(10, 20),
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(13, 15),
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(4, 31),
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(10, 42),
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(43, 34),
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(5, 12),
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(12, 25),
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(10, 25),
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(6, 9),
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]
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expected_results = [20, 195, 124, 210, 1462, 60, 300, 50, 18]
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def test_lcm_function(self):
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for i, (first_num, second_num) in enumerate(self.test_inputs):
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slow_result = least_common_multiple_slow(first_num, second_num)
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fast_result = least_common_multiple_fast(first_num, second_num)
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with self.subTest(i=i):
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self.assertEqual(slow_result, self.expected_results[i])
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self.assertEqual(fast_result, self.expected_results[i])
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if __name__ == "__main__":
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benchmark()
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unittest.main()
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