String-686-Repeated String Match

Description:
Given two strings A and B, find the minimum number of times A has to be repeated such that B is a substring of it. If no such solution, return -1.

For example, with A = “abcd” and B = “cdabcdab”.

Return 3, because by repeating A three times (“abcdabcdabcd”), B is a substring of it; and B is not a substring of A repeated two times (“abcdabcd”).

Note:
The length of A and B will be between 1 and 10000.

solution:

class Solution {
    public int repeatedStringMatch(String A, String B) {
        int q = 1;
        StringBuilder S = new StringBuilder(A);
        for (; S.length() < B.length(); q++) S.append(A);
        if (S.indexOf(B) >= 0) return q;
        if (S.append(A).indexOf(B) >= 0) return q+1;
        return -1;
    }
}