C++ Program to check whether one string is a rotation of another

January 11, 2022

Program to check whether one string is a rotation of another

Today in this article we will discuss how to check whether one string is a rotation of another string, We will also disscuss various methods to do the porblem .

Lets understand this with the help of example :-

Input:-

String1= ABCDA ,String2= DAABC

Output:- Yes

temp = string1.string1 = “ABCDAABCDA ” Since string2 is a substring of temp, string1 and string2 are rotations of each other.

Algorithm

Take two string input from the user a and b respectively.
Write a function checkRotation(string a,string b) that will take the two strings as parameters.
Check if the length of both the sting is equal or not if its not equal then return false
Initialize a temp string that will hold the concatenated string
checking if s2 is present in the temp string if its present initialize flag to 0.
Compare the value of flag if its 1 means the 2nd string is present in temp otherwise return false.

C++ Code :-

  #include<bits/stdc++.h>

  using namespace std;

  bool checkRotation(string s1, string s2) {

  // checking if the length of the two string is same or not
  if (s1.length() != s2.length())
    return false; //returning false if strings are not equal

  string temp = s1 + s1; //storing concatenated string

  int n = temp.length();
  int m = s2.length();

  // checking if s2 is present in temp
  for(int i = 0; i<n-m; i++)
  {
   int flag = 1, j;
     for(j = 0; j < m-1; j++)
     {
       if(s2[j] != temp[i+j])
       {
        flag = 0;
        break;
      }
    }

   if(flag == 1){ 
    return true; // return true if s2 is present in temp
    }
  }

  return false;
 }

int main() {
  string a, b ;

  //Take two input from the user

  cout<<"Enter string 1 : ";
  getline(cin,a);

  cout<<"Enter string 2 : ";
  getline(cin,b);

  if(checkRotation(a, b))
    cout<<"Given Strings are rotations of each other.";
  else
    cout<<"Given Strings are not rotations of each other.";
 return 0;

}

Output:-

Enter string 1 : ACDA
Enter string 2 : AACD
Strings are rotations of each other

Enter first string : ABAA
Enter second string : ADSA
Strings are not rotations of each other

Method 2

The approach is same here we are using build in function.
We can use build in function to check if the string 2 is present in the concatenated string.

  #include<iostream>
  using namespace std;

  bool checkRotation(string s1, string s2) {

  // checking if the length of the two string is same or not
  if (s1.length() != s2.length())
    return false; //returning false if strings are not equal

  string temp = s1 + s1; //storing concatenated string in temp

  int n = temp.length();
  int m = s2.length();
  int flag = temp.find(s2);

  if(flag == 1){
    return true; // return true if s2 is present in temp
   }
  return false;
 }

  int main() {

   string a, b ;

  cout<<"Enter string 1 : ";
  getline(cin,a);

  cout<<"Enter string 2 : ";
  getline(cin,b);

  if(checkRotation(a, b))
    cout<<"Given Strings are rotations of each other.";
  else
   cout<<"Given Strings are not rotations of each other.";
  return 0;
 }

Output:-

Enter string 1 : ABCA
Enter string 2 : AABX
Given Strings are not rotations of each other.

Enter string 1 : ACDA
Enter string 2 : AACD
Given Strings are rotations of each other.