686. Repeated String Match

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").

 

public int repeatedStringMatch(String A, String B) {

    int count = 0;
    StringBuilder sb = new StringBuilder();
    while (sb.length() < B.length()) {
        sb.append(A);
        count++;
    }
    if(sb.toString().contains(B)) return count;
    if(sb.append(A).toString().contains(B)) return ++count;
    return -1;
}