Skip to content

Handle zero and negative inputs in least common multiple implementations #14242

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
Tithi234 wants to merge 2 commits into
base: master
Choose a base branch
from
Open

Handle zero and negative inputs in least common multiple implementations #14242

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
750c1cc
fix: handle zero and negative inputs in least common multiple
Tithi234 Feb 4, 2026
70ed5a7
[pre-commit.ci] auto fixes from pre-commit.com hooks
pre-commit-ci[bot] Feb 4, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
28 changes: 21 additions & 7 deletions maths/least_common_multiple.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6,16 +6,21 @@

def least_common_multiple_slow(first_num: int, second_num: int) -> int:
"""
Find the least common multiple of two numbers.
Find the least common multiple (LCM) of two integers.

Learn more: https://en.wikipedia.org/wiki/Least_common_multiple

>>> least_common_multiple_slow(5, 2)
10
>>> least_common_multiple_slow(12, 76)
228
>>> least_common_multiple_slow(0, 5)
0
"""
max_num = first_num if first_num >= second_num else second_num
if first_num == 0 or second_num == 0:
return 0

max_num = max(abs(first_num), abs(second_num))
common_mult = max_num
while (common_mult % first_num > 0) or (common_mult % second_num > 0):
common_mult += max_num
Expand All @@ -24,14 +29,22 @@ def least_common_multiple_slow(first_num: int, second_num: int) -> int:

def least_common_multiple_fast(first_num: int, second_num: int) -> int:
"""
Find the least common multiple of two numbers.
Find the least common multiple (LCM) of two integers.

Uses the relationship between LCM and GCD:
https://en.wikipedia.org/wiki/Least_common_multiple#Using_the_greatest_common_divisor
>>> least_common_multiple_fast(5,2)

>>> least_common_multiple_fast(5, 2)
10
>>> least_common_multiple_fast(12,76)
>>> least_common_multiple_fast(12, 76)
228
>>> least_common_multiple_fast(0, 5)
0
"""
return first_num // greatest_common_divisor(first_num, second_num) * second_num
if first_num == 0 or second_num == 0:
return 0

return abs(first_num // greatest_common_divisor(first_num, second_num) * second_num)


def benchmark():
Expand Down Expand Up @@ -59,8 +72,9 @@ class TestLeastCommonMultiple(unittest.TestCase):
(12, 25),
(10, 25),
(6, 9),
(0, 5),
)
expected_results = (20, 195, 124, 210, 1462, 60, 300, 50, 18)
expected_results = (20, 195, 124, 210, 1462, 60, 300, 50, 18, 0)

def test_lcm_function(self):
for i, (first_num, second_num) in enumerate(self.test_inputs):
Expand Down
Loading