1071. Greatest Common Divisor of Strings

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

Description

For two strings s and t, we say "t divides s" if and only if s = t + ... + t (t concatenated with itself 1 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:** ""

Example 4:

**Input:** str1 = "ABCDEF", str2 = "ABC"
**Output:** ""

Constraints:

• 1 <= str1.length <= 1000

• 1 <= str2.length <= 1000

• str1 and str2 consist of English uppercase letters.

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