1: 1071. Greatest Common Divisor of Strings.py

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

# solution:
class Solution:
    def gcdOfStrings(self, str1: str, str2: str) -> str:
        # Check if they have non-zero GCD string.
        if str1 + str2 != str2 + str1:
            return ""

        # Get the GCD of the two lengths.
        max_length = gcd(len(str1), len(str2))
        return str1[:max_length]