String rotation interview question for 5 Years of exprience

After long time I have got time to update my blog and help to the followers. These are the most commonly asking interview questions in string concept in java.

String Rotation:
How can you find one string is the rotation of another string?

As we all know what the rotation means is, moving the first character of the string into last. When you keep doing the same, after certain moves you will get the initial string. This is what String Rotation is.

Let say I have two strings as mentioned in the below,
String str1 = “ABCDEF”;
String str2 = “DEFABC”;

Now, apply your logic to find str1 is the rotation of str2 or in reverse. First try your own, if not follow the below logic. This is also one of the CMMI Level5 company interview question.

Steps to solve the above problem:
  1. If you want to find str1 is the rotation of str2. Let’s do concatenation of str2 with it. Means String str3 = str2+str2;
  2. Find the str3 contains the str1 or not by using the contains () method of the String class. str3.contains(str1);
  3. It will return true or false only….If you get true it is rotation string only.
Complete Logic:

public class StringRotation {

 public static void main(String[] args) {
  String str1 = "DEFABC";
  String str2 = "ABCDEF";

  String str3 = str2 + str2;
  if (str3.contains(str1)) {
   System.out.println(str1 + " is the rotation of " + str2);
  } else {
   System.out.println(str1 + " is not the rotation of " + str2);
  }
 }
}


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