1071. Greatest Common Divisor of Strings

Easy

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.

解題

func gcdOfStrings(str1 string, str2 string) string {
    l := gcd(len(str1), len(str2))
    
    if str1[:l] != str2[:l] {
        return ""
    }

    for i:=0; i<=len(str1)-l; i+=l {
        if str1[i:i+l] != str1[:l] {
            return ""
        }
    } 

    for i:=0; i<=len(str2)-l; i+=l {
        if str2[i:i+l] != str2[:l] {
            return ""
        }
    } 

    return str1[:l]
}

func gcd(a, b int) int {
    if b == 0 { return a }
    return gcd(b, a % b)
}