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Php Program for Minimum rotations required to get the same string

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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. 


// 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!
Auxiliary Space: O(n), The extra space is used to store the copied string in tmp variable.

Last Updated : 27 Dec, 2022
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