How to Efficiently Determine if a String is a Palindrome?

How to Effectively Check Strings for Palindromes

Checking strings for palindromes involves verifying whether they read identically in both directions. A straightforward approach to this task is to convert the string into a character array and compare adjacent elements.

Here's a sample implementation of this approach:

public class Aufg1 {
    // Main method for testing
    public static void main(String[] args) {
        String wort = "reliefpfpfeiller";
        char[] warray = wort.toCharArray();
        System.out.println(istPalindrom(warray));
    }

    // Method for checking palindromes
    public static boolean istPalindrom(char[] word) {
        boolean palindrom = false;
        if (word.length % 2 == 0) {
            for (int i = 0; i < word.length / 2 - 1; i++) {
                if (word[i] != word[word.length - i - 1]) {
                    return false;
                } else {
                    palindrom = true;
                }
            }
        } else {
            for (int i = 0; i < (word.length - 1) / 2 - 1; i++) {
                if (word[i] != word[word.length - i - 1]) {
                    return false;
                } else {
                    palindrom = true;
                }
            }
        }
        return palindrom;
    }
}

This code iterates over the character array, comparing elements at opposite ends to determine if they match. However, a more optimized approach exists that involves comparing elements starting from the beginning and end simultaneously.

Improved Code:

public static boolean istPalindrom(char[] word) {
    int i1 = 0;
    int i2 = word.length - 1;
    while (i2 > i1) {
        if (word[i1] != word[i2]) {
            return false;
        }
        ++i1;
        --i2;
    }
    return true;
}

Example:

Using the input string "andna" as an example:

• Initialize i1 to 0 (representing the beginning of the string) and i2 to 4 (representing the end).
• The loop compares word[0] (a) with word[4] (a).
• i1 is incremented to 1 while i2 is decremented to 3.
• The loop continues, comparing word[1] (n) with word[3] (n).
• i1 is incremented to 2 while i2 is decremented to 2.
• Now, i1 is equal to i2, so the loop terminates and the function returns true, indicating that the string is a palindrome.

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