<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) {
        // Reverse the original string
        string reversedString = string(s.rbegin(), s.rend());

        // Combine the original and reversed strings with a separator
        string combinedString = s + "#" + reversedString;

        // Build the prefix table for the combined string
        vector<int> prefixTable = buildPrefixTable(combinedString);

        // Get the length of the longest palindromic prefix
        int palindromeLength = prefixTable[combinedString.length() - 1];

        // Construct the shortest palindrome by appending the reverse of the
        // suffix
        string suffix = reversedString.substr(0, s.length() - palindromeLength);
        return suffix + s;
    }

private:
    // Helper function to build the KMP prefix table
    vector<int> buildPrefixTable(const string& s) {
        vector<int> prefixTable(s.length(), 0);
        int length = 0;

        // Build the table by comparing characters
        for (int i = 1; i < s.length(); i++) {
            while (length > 0 && s[i] != s[length]) {
                length = prefixTable[length - 1];
            }
            if (s[i] == s[length]) {
                length++;
            }
            prefixTable[i] = length;
        }
        return prefixTable;
    }
};
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