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Python3 Program for Minimum rotations required to get the same string

  • Last Updated : 11 Jan, 2022

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.

Python3




# 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.


Output:
3

Time Complexity: O(n2)

Alternate Implementation in Python :

Python3




# 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.


Output:
1

Please refer complete article on Minimum rotations required to get the same string for more details!


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