Palindrome Test with Recursive Method

Question

I was assigned in class to do make a program containing a recursive method that tests if the user's input is a palindrome. My instructor helped us out by giving us some lines of code for us to complete, however rather than helping me, they've only confused me...
package project6;
public class Palindrome {
void main(String[] args) {
        // TODO code application logic here
        char charArray[] = args[0].toCharArray();
    public static Boolean testPalindrome(char[] text, int beg, int end) {
        //First case: the fragment in question is empty
        //This will be the case if beg is > end
        if(beg > end)
            return true;
        //Second case: the fragment contains just one character
        //This will be the case when beg == end.
        if(beg == end)
            return true;
        //Third case: is it of the form "x" + s + "x"
        if(testPalindrome(??, ?, ?))
        else
        return false;
}Firstly,
        if(beg > end)
            return true;How does this statement check if the array is empty? And why use >? Shouldn't it be == ?
Secondly,
        if(beg == end)
            return true;I understand this it to test if there is only 1 character, but don't palindromes with more than 1 character have the same beg and end? So why do this test?
Thirdly,
I don't get why a recursive function is necessary. Wouldn't it be much easier to store the input text into 2 arrays one in its original form and reversed form, and compare the two if they are identical?
I would do that, but he wants our class to follow his way ...

Answer 1

onguy3n wrote:
I don't get why a recursive function is necessary. Wouldn't it be much easier to store the input text into 2 arrays one in its original form and reversed form, and compare the two if they are identical?
I would do that, but he wants our class to follow his way ...I guess your teacher wants to you to learn the recursive way of thinking in this exercise
I'm gonna give u the algorithm of the code your supposed to implement.
boolean isPalindrome(char[] x,int begin,int end)
//if x[begin] equals to x[end]
// return isPalindrome(x,begin+1,end-1)
// else return false
}Now every recursive function will need a terminal condition , this should go right at the beginning of the method. Your terminal condition(s) should be
//if begin>=end return trueAnd yea , ur inital call to the function should be isPalindrome(original array , 0, original array -1)
Edited by: darth_code_r on Nov 24, 2008 2:50 PM