1071. Greatest Common Divisor of Strings

Problem Link

Description

---

For two strings s and t, we say "t divides s" if and only if s = t + t + t + ... + 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.

Solution

---

Python3

class Solution:
    def gcdOfStrings(self, A: str, B: str) -> str:
        if len(A) == len(B):
            return A if A == B else ""
        
        if len(A) < len(B):
            A, B = B, A
        
        if A[:len(B)] == B:
            return self.gcdOfStrings(A[len(B):], B)
        else:
            return ""