一、题目

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.

二、题解

注意substr函数与__gcd(a,b)函数的用法

class Solution {
public:string gcdOfStrings(string str1, string str2) {int n1 = str1.length();int n2 = str2.length();if(str1 + str2 != str2 + str1) return "";else return str1.substr(0,__gcd(n1,n2));}
};