686. Repeated String Match

// 实话实说没觉得特别easy。。
class Solution {
    public int repeatedStringMatch(String A, String B) {
        if(A == null || B == null) return -1;
        if(B.equals("")) return 1;
        int m = A.length(), n = B.length(), count = 0;
        StringBuilder sb = new StringBuilder();
        while(sb.length() < n)
        {
            sb.append(A);
            count++;
        }
        if(sb.indexOf(B) >= 0) return count;
        if(sb.append(A).indexOf(B) >= 0) return count + 1;
        return -1;
    }
}