Minimum rotations required to get the same string

Given a string, we need to find the minimum number of rotations required to get the same string.

Examples:

Input : s = "geeks"
Output : 5

Input : s = "aaaa"
Output : 1

The idea is based on below post.

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




Step 1 :
Initialize result = 0 (Here result is count of rotations)
Step 2 : Take a temporary string equals to original string concatenated with itself.
Step 3 : Now take the substring of temporary string of size same as original string starting from second character (or index 1).
Step 4 : Increase the count.
Step 5 : Check whether the substring becomes equal to original string. If yes, then break the loop. Else go to step 2 and repeat it from the next index.

C/C++

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// C++ program to determine minimum number
// of rotations required to yield same
// string.
#include <iostream>
using namespace std;
  
// Returns count of rotations to get the
// same string back.
int findRotations(string str)
{
    // tmp is the concatenated string.
    string tmp = str + str;
    int n = str.length();
  
    for (int i = 1; i <= n; i++) {
  
        // substring from i index of original
        // string size.
        string substring = tmp.substr(i, str.size());
  
        // if substring matches with original string
        // then we will come out of the loop.
        if (str == substring)
            return i;
    }
    return n;
}
  
// Driver code
int main()
{
    string str = "abc";
    cout << findRotations(str) << endl;
    return 0;
}

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Java

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// Java program to determine minimum number 
// of rotations required to yield same 
// string. 
  
import java.util.*; 
  
class GFG 
    // Returns count of rotations to get the 
    // same string back. 
    static int findRotations(String str) 
    
        // tmp is the concatenated string. 
        String tmp = str + str; 
        int n = str.length(); 
      
        for (int i = 1; i <= n; i++) 
        
      
            // substring from i index of original 
            // string size. 
              
            String substring = tmp.substring(
                    i, i+str.length()); 
      
            // if substring matches with original string 
            // then we will come out of the loop. 
            if (str.equals(substring)) 
                return i; 
        
        return n; 
    
  
    // Driver Method 
    public static void main(String[] args) 
    
            String str = "aaaa"
        System.out.println(findRotations(str)); 
    
/* This code is contributed by Mr. Somesh Awasthi */

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Python3

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# Python 3 program to determine minimum 
# number of rotations required to yield 
# same string.
  
# Returns count of rotations to get the
# same string back.
def findRotations(str):
      
    # tmp is the concatenated string.
    tmp = str + str
    n = len(str)
  
    for i in range(1, n + 1):
          
        # substring from i index of 
        # original string size.
        substring = tmp[i: i+n]
  
        # if substring matches with 
        # original string then we will 
        # come out of the loop.
        if (str == substring):
            return i
    return n
  
# Driver code
if __name__ == '__main__':
  
    str = "abc"
    print(findRotations(str))
  
# This code is contributed 
# by 29AjayKumar.

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C#

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// C# program to determine minimum number
// of rotations required to yield same
// string.
using System;
  
class GFG {
      
    // Returns count of rotations to get
    // the same string back.
    static int findRotations(String str)
    {
          
        // tmp is the concatenated string.
        String tmp = str + str;
        int n = str.Length;
      
        for (int i = 1; i <= n; i++)
        {
      
            // substring from i index of
            // original string size.
              
            String substring = 
                 tmp.Substring(i, str.Length);
      
            // if substring matches with
            // original string then we will
            // come out of the loop.
            if (str == substring)
                return i;
        }
          
        return n;
    }
  
    // Driver Method
    public static void Main()
    {
        String str = "abc";
          
        Console.Write(findRotations(str));
    }
}
  
// This code is contributed by nitin mittal.

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PHP

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<?php
// PHP program to determine minimum 
// number of rotations required to 
// yield same string. 
  
// Returns count of rotations 
// to get the same string back. 
function findRotations($str
    // tmp is the concatenated string. 
    $tmp = ($str + $str); 
    $n = strlen($str); 
  
    for ( $i = 1; $i <= $n; $i++)
    
  
        // substring from i index 
        // of original string size. 
        $substring = $tmp.substr($i
                          strlen($str)); 
  
        // if substring matches with 
        // original string then we will 
        // come out of the loop. 
        if ($str == $substring
            return $i
    
    return $n
  
// Driver code 
$str = "abc"
echo findRotations($str), "\n"
  
// This code is contributed 
// by Sachin
?>

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Output:

3

Time Complexity: O(n2)

Alternate Implementation in Python :

Python3

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# Python 3 program to determine minimum 
# number of rotations required to yield 
# same string.
   
# input
string = 'aaaa'
check = ''
   
for r in range(1, len(string)+1):
  # checking the input after each rotation
  check = string[r:] + string[:r]
     
  # following if statement checks if input is 
  # equals to check , if yes it will print r and 
  # break out of the loop
  if check == string:
    print(r)
    break
   
# This code is contributed 
# by nagasowmyanarayanan.

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Output:

1

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