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++
// 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; } |
Java
// 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 */ |
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. |
C#
// 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. |
PHP
<?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 ?> |
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
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