README_EN.md

01.09. String Rotation

Description

Given two strings, s1 and s2, write code to check if s2 is a rotation of s1 (e.g.,"waterbottle" is a rotation of"erbottlewat"). Can you use only one call to the method that checks if one word is a substring of another?

Example 1:

Input: s1 = "waterbottle", s2 = "erbottlewat"

Output: True

Example 2:

Input: s1 = "aa", "aba"

Output: False

 

Note:

1. 0 <= s1.length, s1.length <= 100000

Solutions

Java

class Solution {
    public boolean isFlipedString(String s1, String s2) {
        int len1 = s1.length(), len2 = s2.length();
        if (len1 != len2) {
            return false;
        }
        if ((len1 == 0 && len2 == 0) || (s1.equals(s2))) {
            return true;
        }

        for (int i = 0; i < len1; ++i) {
            s1 = flip(s1);
            if (s1.equals(s2)) {
                return true;
            }
        }
        return false;

    }

    private String flip(String s) {
        return s.substring(1) + s.charAt(0);
    }
}

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