Leetcode 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.

Easy 题目，还是不是substring的函数，看了大神的代码，真的获益匪浅，我的代码真的太low了。2个字符串翻转合并看是否一样，不一样返回false，一样的话，再求2个字符串的长度的最大公约数即可；

Runtime: 33 ms, faster than 5.05% of Java online submissions for Greatest Common Divisor of Strings.

Memory Usage: 42.6 MB, less than 9.09% of Java online submissions for Greatest Common Divisor of Strings.