1.8---字符串是否是旋转而成（CC150）

答案：利用了XY , YX中第一个XYXY包含了第二个

public class Solution{
    
    public static void main(String[] args){
        System.out.println(isRotation("abc","abc"));
    }
    public static boolean isSubstring(String str1,String str2){
        if(str1.contains(str2) || str2.contains(str1))    return true;
        
        
        return false;
    }
    public static boolean isRotation(String str1,String str2){
        if(str1.length() != str2.length()) return false;
        String sum = str1 + str1;
        return isSubstring(sum,str2);
    }
}