<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:
    def shortestPalindrome(self, s: str) -> str:
        rev = s[::-1]
        mid = len(s)

        s = s + "$"+rev
        L = 0
        R = 0
        n = len(s)
        
        Z = [0] * n
        ans = 0
        for i in range(1,n):
            if(i > R):
                L=i
                R=i
                while(R<n and s[R-L] == s[R]):
                    R += 1
                Z[i] = R-L

                R-= 1
            else:
                k = i-L
                if Z[k] >=  R-i+1:
                    L=i
                    while(R<n and s[R-L] == s[R]):
                        R += 1
                    Z[i] = R-L

                    R-= 1
                else:
                    Z[i] = Z[k]
            if R == n-1:
                ans = L
                break

        #print()
        return s[mid+1:ans]+s[0:mid]

            
        #print(s)
        
19100