面试题 01.09. String Rotation LCCI

Problem

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?

Example1

Input: s1 = “waterbottle”, s2 = “erbottlewat”
Output: True

Example2

Input: s1 = “aa”, “aba”
Output: False

Solution

首先，长度不一样，肯定不是。

s1 = waterbottle，s2= erbottlewat。
另x = wat，y=erbottle，则s1 = xy，s2=yx。
如果将两个s2串接在一起，可以得到s=s2+s2 = yxyx，中间有xy=s1。

class Solution {
public:
    bool isFlipedString(string s1, string s2) {
        if(s1.length() != s2.length())
            return false;
        
        string s = s2 + s2;
        return s.find(s1) != string::npos ;

    }
};