Number of Common Factors — LeetCode 2427 Python Solution

The problem

Given two positive integers a and b, return the number of common factors of a and b. An integer x is a common factor of a and b if x divides both a and b.

Example

Input

a = 12, b = 6

Output

4

Explanation

The common factors of 12 and 6 are 1, 2, 3, 6.

Python solution

class Solution:
    def commonFactors(self, a: int, b: int) -> int:
        g = gcd(a, b)
        return sum(g % x == 0 for x in range(1, g + 1))

Complexity

Pattern: Math and Number Theory

Find the closed form, the invariant, or the modular identity — and skip the loop entirely. LeetCode 2427. Number of Common Factors is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Math and Number Theory.

The math and number theory guide has the Python template for the pattern and the 485 LeetCode problems that use it.

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