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Recursion for Coding Interviews in Java

Solution Review: Is this String a Palindrome?

Explore how to determine if a string is a palindrome through recursive programming. This lesson guides you through understanding base cases and recursive calls in the palindrome check to strengthen your skills in recursion with strings.

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Solution: Palindrome or not?

Java
class ChallengeClass {
    public static boolean isPalindrome(String text) {
        if (text.length() <= 1) {
            return true;
        }
        else {
            if (text.charAt(0) == text.charAt(text.length()-1)) {
                return isPalindrome(text.substring(1, text.length()-1));
            }
        }
        return false;
    }
    public static void main( String args[] ) { 
        String input1 = "hello";
        String input2 = "dadad";
        boolean answer1 = isPalindrome(input1);
        boolean answer2 = isPalindrome(input2);
        System.out.println("Is " + input1 + " a Palindrome? = " + answer1);
        System.out.println("Is " + input2 + " a Palindrome? = " + answer2);
    }  
}

Understanding the Code

Every recursive code has two methods: the recursive method and the main method.

Driver Method

The recursive method is called within the driver method. Let’s first look at what it does-from line 19 to 24.

  • In this driver method, we have two strings where input2 is a palindrome and input1 is not.

  • For each string, it calls on the isPalindrome method, and the output of the method is stored in the answer1 and answer2 variables. ...