<p>You are given a string <code>s</code>. You can convert <code>s</code> to a <span data-keyword="palindrome-string">palindrome</span> by adding characters in front of it.</p>

<p>Return <em>the shortest palindrome you can find by performing this transformation</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<pre><strong>Input:</strong> s = "aacecaaa"
<strong>Output:</strong> "aaacecaaa"
</pre><p><strong class="example">Example 2:</strong></p>
<pre><strong>Input:</strong> s = "abcd"
<strong>Output:</strong> "dcbabcd"
</pre>
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>0 &lt;= s.length &lt;= 5 * 10<sup>4</sup></code></li>
	<li><code>s</code> consists of lowercase English letters only.</li>
</ul>

class Solution {
public:
    string shortestPalindrome(string s) {
        long long hashBase = 29;
        long long modValue = 1e9 + 7;
        long long forwardHash = 0, reverseHash = 0, powerValue = 1;
        int palindromeEndIndex = -1;

        // Calculate rolling hashes and find the longest palindromic prefix
        for (int i = 0; i < s.length(); ++i) {
            char currentChar = s[i];

            // Update forward hash
            forwardHash =
                (forwardHash * hashBase + (currentChar - 'a' + 1)) % modValue;

            // Update reverse hash
            reverseHash =
                (reverseHash + (currentChar - 'a' + 1) * powerValue) % modValue;
            powerValue = (powerValue * hashBase) % modValue;

            // If forward and reverse hashes match, update palindrome end index
            if (forwardHash == reverseHash) {
                palindromeEndIndex = i;
            }
        }

        // Find the remaining suffix after the longest palindromic prefix
        string suffix = s.substr(palindromeEndIndex + 1);
        // Reverse the remaining suffix
        string reversedSuffix(suffix.rbegin(), suffix.rend());

        // Prepend the reversed suffix to the original string and return the
        // result
        return reversedSuffix + s;
    }
};
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