A Program to check if strings are rotations of each other or not?

Here we will see one program that can tell whether two strings are rotation of each other or not. The rotation of strings is like −

Suppose two strings are S1 = ‘HELLO’, and S2 = ‘LOHEL’ So they are rotation of each other. By rotating HELLO three position to the left it will be LOHEL.

To solve this problem, we will concatenate the first string with itself, then check whether the second one is present in the concatenated string or not. So for HELLO, it will be HELLOHELLO. Then this concatenated string contains the LOHEL. [HELLOHELLO].

Algorithm

isRotation(str1, str2)

begin
   if lengths of str1, and str2 are not same then return false;
   temp := concatenate str1 with str1 itself
   if temp contains str2, then
      return true
   otherwise return false
end

Example

 Live Demo

#include<iostream>
using namespace std;
bool isRotation(string str1, string str2){
   if(str1.length() != str2.length())
      return false;
   string con_str = str1 + str1;
   if(con_str.find(str2) != string::npos){
      return true;
   } else {
      return false;
   }
}
main() {
   string str1, str2;
   cout << "Enter two strings: ";
   cin >> str1 >> str2;
   if(isRotation(str1, str2)){
      cout << "Two strings are rotation of each other";
   } else {
      cout << "Two strings are not rotation of each other";
   }
}

Output

Enter two strings: STACK CKSTA
Two strings are rotation of each other