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Php 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.


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.


// 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
        // 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), "
// This code is contributed 
// by Sachin


Time Complexity: O(n2)

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

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