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1071. Greatest Common Divisor of Strings

Basant Babu Bhandari's photo
Basant Babu Bhandari
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1 min read

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:

class Solution:
    def gcdOfStrings(self, str1: str, str2: str) -> str:
        len1, len2 = len(str1), len(str2)

        def isDivisor(l):
            if len1 % l or len2 % l:
                return False

            f1, f2 = len1 // l , len2 // l
            return str1[:l]*f1 == str1 and str1[:l]*f2 == str2

        for l in range(min(len1, len2), 0, -1):
            if isDivisor(l):
                return str1[:l]

        return ""
DSA