796. Rotate String

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.

如果把A的一部分子串移到后面，跟B相等，则返回true

C++（3ms）：

1 class Solution {
2 public:
3     bool rotateString(string A, string B) {
4         return (A.size() == B.size() && (A+A).find(B) != string::npos) ;
5     }
6 };