[leetcode]796. Rotate String旋转字串

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

题意

给定字串A和B， 问是否能通过旋转使得二者相等

Solution1：StringBuilder

直到 A和B 相等，return true， 退出循环

   

code

class Solution {
    public static boolean rotateString(String A, String B) {
        if (A.length() != B.length()) {
            return false;
        }
        if (A.length() == 0) {
            return true;
        }
        StringBuilder sb = new StringBuilder(B);

        for (int i = 0; i < B.length(); i++) { 
            if (A.equals(B)) {return true; }
            char c = sb.charAt(0);
            sb.deleteCharAt(0);
            sb.append(c);
            B = sb.toString();
        }
        return false;
    }
}