[LeetCode] Rotate String

Problem

We are given two strings, A and B.

A shift on A consists of taking string A and moving the leftmost character to the rightmost position. For example, if A = 'abcde', then it will be 'bcdea' after one shift on A. Return True if and only if A can become B after some number of shifts on A.

Example 1:
Input: A = 'abcde', B = 'cdeab'
Output: true

Example 2:
Input: A = 'abcde', B = 'abced'
Output: false
Note:

A and B will have length at most 100.

Solution

class Solution {
    public boolean rotateString(String A, String B) {
        // if (A == null) return B == null;
        // if (B == null) return A == null;
        if (A.length() == 0) return B.length() == 0;
        if (A.length() != B.length()) return false;
        String AA = new String(A+A);
        for (int i = 0; i < A.length(); i++) {
            if (AA.substring(i, i+A.length()).equals(B)) return true;
        }
        return false;
    }
}