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Check if left and right shift of any string results into given string

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Given string S consisting of only lowercase English letters. The task is to find if there exists any string which has left shift and right shift both equal to string S. If there exists any string then print Yes, otherwise print No.

Examples: 

Input: S = “abcd” 
Output: No 
Explanation: 
There is no string which have left shift and right shift both equal to string “abcd”.

Input: papa 
Output: Yes 
Explanation: 
The left shift and right shift both of string “apap” equals to string “papa”. 
 

Approach: 

  1. The main target is to check the left shift and right shift both of any string equals to given string or not.
  2. For that we just have to check every character of given string is equal to its next to next character or not (i.e. character at (i)th position must be equal to character at (i+2)th position ).
  3. If it’s true for every position on the given string then we can say there exist any string whose left shift and right shift equal to given string otherwise not.

Below is the implementation of the above approach: 

C++




// C++ program to check if left
// and right shift of any string
// results into the given string
 
#include <bits/stdc++.h>
using namespace std;
 
// Function to check string exist
// or not as per above approach
void check_string_exist(string S)
{
    int size = S.length();
 
    bool check = true;
 
    for (int i = 0; i < size; i++) {
 
        // Check if any character
        // at position i and i+2
        // are not equal
        // then string doesnot exist
        if (S[i] != S[(i + 2) % size]) {
            check = false;
            break;
        }
    }
 
    if (check)
        cout << "Yes" << endl;
    else
        cout << "No" << endl;
}
 
// Driver code
int main()
{
    string S = "papa";
 
    check_string_exist(S);
 
    return 0;
}


Java




// Java program to check if left
// and right shift of any string
// results into the given string
class GFG{
     
// Function to check string exist
// or not as per above approach
public static void check_string_exist(String S)
{
    int size = S.length();
    boolean check = true;
     
    for(int i = 0; i < size; i++)
    {
        
       // Check if any character
       // at position i and i+2
       // are not equal
       // then string doesnot exist
       if (S.charAt(i) != S.charAt((i + 2) % size))
       {
           check = false;
           break;
       }
    }
     
    if (check)
        System.out.println("Yes");
    else
        System.out.println("No");
}
 
// Driver Code
public static void main(String[] args)
{
    String S = "papa";
     
    check_string_exist(S);
}
}
 
// This code is contributed by divyeshrabadiya07


Python3




# Python3 program to check if left
# and right shift of any string
# results into the given string
 
# Function to check string exist
# or not as per above approach
def check_string_exist(S):
     
    size = len(S)
    check = True
     
    for i in range(size):
         
        # Check if any character
        # at position i and i+2
        # are not equal, then 
        # string doesnot exist
        if S[i] != S[(i + 2) % size]:
            check = False
            break
         
    if check :
        print("Yes")
    else:
        print("No")
 
# Driver Code
S = "papa"
 
check_string_exist(S)
 
# This code is contributed by divyeshrabadiya07


C#




// C# program to check if left
// and right shift of any string
// results into the given string
using System;
 
class GFG{
     
// Function to check string exist
// or not as per above approach
public static void check_string_exist(String S)
{
    int size = S.Length;
    bool check = true;
     
    for(int i = 0; i < size; i++)
    {
         
       // Check if any character
       // at position i and i+2
       // are not equal
       // then string doesnot exist
       if (S[i] != S[(i + 2) % size])
       {
           check = false;
           break;
       }
    }
    if (check)
        Console.WriteLine("Yes");
    else
        Console.WriteLine("No");
}
 
// Driver Code
public static void Main(String[] args)
{
    String S = "papa";
     
    check_string_exist(S);
}
}
 
// This code is contributed by sapnasingh4991


Javascript




<script>
 
// Javascript program to check if left
// and right shift of any string
// results into the given string
 
// Function to check string exist
// or not as per above approach
function check_string_exist(S)
{
    var size = S.length;
 
    var check = true;
 
    for (var i = 0; i < size; i++) {
 
        // Check if any character
        // at position i and i+2
        // are not equal
        // then string doesnot exist
        if (S[i] != S[(i + 2) % size]) {
            check = false;
            break;
        }
    }
 
    if (check)
        document.write( "Yes" );
    else
        document.write( "No" );
}
 
// Driver code
var S = "papa";
check_string_exist(S);
 
// This code is contributed by noob2000.
</script>


Output

Yes









Time Complexity: O(N) where N is the size of the string S.
Auxiliary Space Complexity: O(1)

Approach: Rotation

In this approach concatenate the input string with itself, and then check if the input string is a substring of the 
concatenated string starting from any position. If we find such a position, it means that the input string can be obtained by
rotating some characters to the left or right.

Below is the implementation of the above approach: 

C++




// C++ program of the above approach
 
#include <iostream>
#include <string>
 
using namespace std;
 
// Function to check if there exists a string which has left
// shift and right shift both equal to the input string
bool isLeftRightShiftEqual(string s)
{
    int n = s.length();
    // Concatenate the input string with itself
    string concatenated = s + s;
    for (int i = 1; i < n; i++) {
        if (s == concatenated.substr(i, n)) {
            return true;
        }
    }
    return false;
}
 
// Driver Code
int main()
{
    string s = "papa";
    if (isLeftRightShiftEqual(s)) {
        cout << "Yes" << endl;
    }
    else {
        cout << "No" << endl;
    }
    return 0;
}


Java




// Java code
 
import java.io.*;
 
public class LeftRightShiftEqual {
    // Function to check if there exists a string
    // which has left shift and right shift both equal to the input string
    public static boolean isLeftRightShiftEqual(String s) {
        int n = s.length();
        // Concatenate the input string with itself
        String concatenated = s + s;
        for (int i = 1; i < n; i++) {
            if (s.equals(concatenated.substring(i, i + n))) {
                return true;
            }
        }
        return false;
    }
 
    public static void main(String[] args) {
        String s = "papa";
        if (isLeftRightShiftEqual(s)) {
            System.out.println("Yes");
        } else {
            System.out.println("No");
        }
    }
}
 
// This code is contributed by guptapratik


Python3




# Python code
 
#Function to check if there exists a string which has left
#shift and right shift both equal to the input string
def isLeftRightShiftEqual(s):
    n = len(s)
    # Concatenate the input string with itself
    concatenated = s + s
    for i in range(1, n):
        if s == concatenated[i:i+n]:
            return True
    return False
 
# Driver Code
if __name__ == "__main__":
    s = "papa"
    if isLeftRightShiftEqual(s):
        print("Yes")
    else:
        print("No")
 
# This code is contributed by guptapratik


C#




using System;
 
namespace LeftRightShiftEqual
{
    class Program
    {
        // Function to check if there exists a string which has left
        // shift and right shift both equal to the input string
        static bool IsLeftRightShiftEqual(string s)
        {
            int n = s.Length;
            // Concatenate the input string with itself
            string concatenated = s + s;
            for (int i = 1; i < n; i++)
            {
                if (s == concatenated.Substring(i, n))
                {
                    return true;
                }
            }
            return false;
        }
 
        // Driver Code
        static void Main(string[] args)
        {
            string s = "papa";
            if (IsLeftRightShiftEqual(s))
            {
                Console.WriteLine("Yes");
            }
            else
            {
                Console.WriteLine("No");
            }
        }
    }
}


Javascript




// Function to check if there exists a string
// which has left shift and right shift both equal to the input string
function isLeftRightShiftEqual(s) {
    let n = s.length;
    // Concatenate the input string with itself
    let concatenated = s + s;
    for (let i = 1; i < n; i++) {
        if (s === concatenated.substring(i, i + n)) {
            return true;
        }
    }
    return false;
}
 
// Main function
function main() {
    let s = "papa";
    if (isLeftRightShiftEqual(s)) {
        console.log("Yes");
    } else {
        console.log("No");
    }
}
 
// Call the main function
main();


Output

Yes










Time Complexity: O(n^2), where n is the length of the input string.

Auxiliary Space: O(n)



Last Updated : 20 Oct, 2023
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