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copied!<p>A non-recursive method that runs under or at O(n/2) in the worst-case (full search). This is more performant when the String is a LONG one... Here's the implementation...</p> <pre><code>class PalindromeClass { /** * This method will run under or at O(n/2) with n = sentence.size() * @param sentence is a given String sentence. * @return true if the given sentence is a palindrome. */ public static boolean isPalindrome(String sentence) { sentence = sentence.replaceAll("[^a-zA-Z0-9]","").toLowerCase(); char[] sentenceChars = sentence.toCharArray(); for (int i = 0; i < sentenceChars.length / 2; i++) { if (sentenceChars[i] != sentenceChars[sentenceChars.length - 1 - i]) { return false; } } return true; } </code></pre> <p>Running this with short, long and with wrong parameters give you the correct values...</p> <pre><code>public static void main(String[] args) { String wrong = "ABCA"; System.out.println("Is '" + wrong + "' a palindrome? "); System.out.println(isPalindrome(wrong)); String none = "A'"; System.out.println("Is '" + none + "' a palindrome? "); System.out.print(isPalindrome(none)); String a = "Madam, I'm Adam"; System.out.println("Is '" + a + "' a palindrome? "); System.out.println(isPalindrome(a)); String b = "abba"; System.out.println("Is '" + b + "' a palindrome? "); System.out.println(isPalindrome(b)); String toyota = "A Toyota. Race fast, safe car. A Toyota."; System.out.println("Is '" + toyota + "' a palindrome? "); System.out.println(isPalindrome(toyota)); String longestPalindrome = "Do good? I? No! Evil anon I deliver. I maim " + "nine more hero-men in Saginaw, sanitary sword a-tuck, Carol, I -- lo! " + "-- rack, cut a drowsy rat in Aswan. I gas nine more hero-men in Miami. " + "Reviled, I (Nona) live on. I do, O God!"; System.out.println("Is '" + longestPalindrome + "' a palindrome? "); System.out.println(isPalindrome(longestPalindrome)); } </code></pre> <p>}</p> <p>Here's the output of the execution...</p> <pre><code>Is 'ABCA' a palindrome? false Is 'a' a palindrome? true Is 'Madam, I'm Adam a palindrome?' true Is 'abba a palindrome? true' Is 'A Toyota. Race fast, safe car. A Toyota.' a palindrome? true Is 'Do good? I? No! Evil anon I deliver. I maim nine more hero-men in Saginaw, sanitary sword a-tuck, Carol, I -- lo! -- rack, cut a drowsy rat in Aswan. I gas nine more hero-men in Miami. Reviled, I (Nona) live on. I do, O God!' a palindrome? true </code></pre>

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