Leetcode 1071. Greatest Common Divisor of Strings

Problem statement

https://leetcode.com/problems/greatest-common-divisor-of-strings/

Solution

First, we check if s1 + s2 == s2 + s1, in this case we know that gcd is not empty. If it is not empty, it is equal to gcd of lengths.

Complexity

It is O(n) for time and space.

Code

class Solution:
    def gcdOfStrings(self, s1, s2):
        return s1[:gcd(len(s1), len(s2))] if s1 + s2 == s2 + s1 else ""