1071. Greatest Common Divisor of Strings.md

1071. Greatest Common Divisor of Strings

For two strings s and t, we say "t divides s" if and only if s = t + ... + t (i.e., t is concatenated with itself one or more times).

Given two strings str1 and str2, return the largest string x such that x divides both str1 and str2.

Example 1:

Input: str1 = "ABCABC", str2 = "ABC"
Output: "ABC"

Example 2:

Input: str1 = "ABABAB", str2 = "ABAB"
Output: "AB"

Example 3:

Input: str1 = "LEET", str2 = "CODE"
Output: ""

Constraints:

• 1 <= str1.length, str2.length <= 1000
• str1 and str2 consist of English uppercase letters. """

Python:

class Solution(object):

    def gcd(self, a, b):
        while b:
            a, b = b, a % b
        return a

    def gcdOfStrings(self, str1, str2):
        """
        :type str1: str
        :type str2: str
        :rtype: str
        """
        len_gcd = self.gcd(len(str1), len(str2))
        str_gcd = str1[:len_gcd]
        if str_gcd * (len(str1) // len_gcd) == str1 and str_gcd * (len(str2) // len_gcd) == str2:
            return str_gcd
        else:
            return ""