1071.go

package main

import "fmt"

func gcdOfStrings(str1 string, str2 string) string {
	if str1+str2 != str2+str1 {
		return ""
	}

	gcdLen := func() int {
		str1Len, str2Len := len(str1), len(str2)
		for str1Len > 0 && str2Len > 0 {
			str1Len %= str2Len
			if str1Len == 0 {
				break
			}
			str1Len, str2Len = str2Len, str1Len
		}
		return str2Len
	}()

	return str1[:gcdLen]
}

func main() {
	fmt.Println(gcdOfStrings("ABCABC", "ABCD"))
	fmt.Println(gcdOfStrings("ABCABC", "ABC"))
	fmt.Println(gcdOfStrings("ABABAB", "ABAB"))
	fmt.Println(gcdOfStrings("ABC", "ABCABC"))
	fmt.Println(gcdOfStrings("ABAB", "ABABAB"))
	fmt.Println(gcdOfStrings("LEET", "CODE"))
	fmt.Println(gcdOfStrings("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA",
		"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"))
}