leetcode-go/leetcode/easy/686.repeated-string-match.go

func repeatedStringMatch(A string, B string) int {
	m, n, l := len(A), len(B), len(A)
	var sb strings.Builder
	for cnt := 1; ; cnt, l = cnt+1, l+m {
		sb.WriteString(A)
		if strings.Index(sb.String(), B) != -1 {
			return cnt
		} else if n + m < l { // If l > n + m, then each repeat of A is the same for B.
			break
		}
	}
	return -1
}