LeetCode|Rotate String

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.

思路：
好像是在《编程珠玑》上面看到过，把A拼接在A后面，即A+A，再去考虑这个问题就简单多了

class Solution {
public:
    bool rotateString(string A, string B) {
        if(A.size() != B.size()) return false;
        if(A.size() == 0) return true; // 两个空串题目认为是true
        string a = A + A.substr(0, A.size()-1);
        for(int i = 0; i < A.size(); ++i){
            if(B == a.substr(i, A.size()))
                return true;
        } return false;
    }
};

discuss上的答案：

bool rotateString(string A, string B) {                
    return A.size() == B.size() && (A + A).find(B) != string::npos;
}