[LeetCode] Problem 686 - Repeated String Match

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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.

Code

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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.indexOf(B) >= 0)
        return count;
    
    return sb.append(A).indexOf(B) >= 0 ? count + 1 : -1;
}