1071. Greatest Common Divisor of Strings -----E

Q:

For strings S and T, we say "T divides S" if and only if S = T + ... + T  (T concatenated with itself 1 or more times)

Return the largest string X such that X divides str1 and X divides 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: ""

 

Note:

1. 1 <= str1.length <= 1000
2. 1 <= str2.length <= 1000
3. str1[i] and str2[i] are English uppercase letters.

A:

class Solution {
public:
    string gcdOfStrings(string str1, string str2) {        
        if(str1 == str2)
            return str1;
        if(str1.length() < str2.length())
            return gcdOfStrings(str2,str1);
        for(int i =0;i<str2.length();i++)
            if(str1[i] != str2[i])
                return "";
        str1 = str1.substr(str2.length(), str1.length()-str2.length());
        return gcdOfStrings(str1, str2);
    }
};