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.

这个题目比较有技巧，因为直接判断B 是否in A + A即可。不过要注意进行length的判断。

class Solution:
    def rotateString(self, s1, s2):
        if len(s1) != len(s2): return False
        return s2 in s1 + s1