Urgent! Need help on Palindrome problem - toCharArray
Started this coding and not sure where to go from here.One of the requirement is the isPal() must take in a char[], int indexNum - that's one of the requirement.
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import java.io.*;
import java.util.StringTokenizer;
public class Palindrome {
private static char[] palindrome;
int sizeOfArray;
private static String text, inText;
public Palindrome()
{
sizeOfArray = 30;
//create an empty array
palindrome = new char[sizeOfArray];
}
public String setPalindrome(String in)
{
StringTokenizer st = new StringTokenizer(in, ".");
text = in;
inText = st.nextToken();
return inText;
}
/*****************************************************************
* a char array containing the characters of the *
* input string, and an integer, number, defining the number of *
* characters in the string *
******************************************************************/
private static boolean isPal(char[] pal, int number)
{
palindrome = pal;
int index = number;
//validate if the character is less than 2 - means that there is only 1 character
if (pal.length< 2)
return true;
//validate if first character == the last position value in the array
//if (pal[0] == pal[pal.length-1])
//return isPal(pal.substring(1, pal.length-1));
return false;
}
public static void main(String[] args)throws IOException
{
String input;
boolean unequal = false;
Palindrome pal = new Palindrome();
//user input
BufferedReader stdin = new BufferedReader (new InputStreamReader (System.in));
System.out.print("Please enter a potential palindrome(enter a period at the end): " );
System.out.flush();
input = stdin.readLine().toLowerCase();
pal.setPalindrome(input);
System.out.println(inText);
//Add input String to a CharArray() - palindrome
palindrome = inText.toCharArray();
int lengthToCheck = palindrome.length/2;
for(int i =0; i<lengthToCheck; i++)
{
if (palindrome[ i ] != palindrome[palindrome.length - (i +1)])
{
unequal = true;
break;
}
//print out the palindrome char[] values.
System.out.println(palindrome);
}
}//end main()
}//end class
>
//Add input String to a CharArray() - palindrome
palindrome = inText.toCharArray();
int lengthToCheck = palindrome.length/2;
for(int i =0; i<lengthToCheck; i++)
{
if (palindrome[ i ] != palindrome[palindrome.length - (i +1)])
{
unequal = true;
break;
}
1.move the above code of yours to isPal and return 'unequal'
2.Call isPal(palindrome, number) in its place.
if( isPal(palindrome,number) ){
System.out.println( inText + " is a palindrome.");
}else{
System.out.println( inText + " is not a palindrome.");
}
3. If the length is 5 you need to loop floor(5/2) = 2
if length is 4 you need to loop floor(4/2) = 2
if length is 9 you need to loop floor(9/2) = 4
because if the number of characters are odd you don't need to compare the middle character any way, so use the floor method of class Math. this method can be called directly on class since it is a statci method.
so do
int lengthToCheck = (int)Math.floor( palindrome.length/2 );
instead of
int lengthToCheck = palindrome.length/2;
>
import java.io.*;
public class test46
{
public static void main(String[] args) throws IOException
{
System.out.print("Please enter the string: ");
BufferedReader stdin = new BufferedReader (new InputStreamReader (System.in));
String str = stdin.readLine().toLowerCase();
if (isPalindrome(str))
{
System.out.println("input string is a palindrome");
}
else
{
System.out.println("input string is not a palindrome");
}
}
public static boolean isPalindrome(String str)
{
boolean retVal = true;
int length = str.length();
if (length < 2)
{
retVal = true;
}
else
{
for(int i = 0; i < length -1; i++)
{
if (str.charAt(i) == str.charAt((length -1) - i)) continue;
else
{
retVal = false;
break;
}
}
}
return retVal;
}
}
Thanks for the info. I actually got it working this morning. But now I am dealing with another problem. My program below is working fine now. But there is this one part I am not sure how to solve. when I receive the string from the buffer reader and before I put that into the toCharArray[],,,I think...I need to disregard blanks when deciding if a string is a palindrome and consider upper and lower case version of the same letter to be equal. I Began to put a piece of code using String Buffer....not sure how to go about further.(see below)
public static void main(String[] args)throws IOException
{
String input;
Palindrome pal = new Palindrome();
//user input
BufferedReader stdin = new BufferedReader (new InputStreamReader (System.in));
System.out.print("Please enter a potential palindrome(enter a period at the end to indicate termination): " );
System.out.flush();
input = stdin.readLine().toLowerCase();
StringBuffer sbuf = new StringBuffer();
for(int j=0; j<input.length(); j++)
{
if (input.charAt(j))
sbuf.append(input.charAt(j));
}
pal.getPalindrome(input);
System.out.println("Input text: " + inText + "\n");
//find out the length of the string
palindrome = inText.toCharArray();
length = palindrome.length;
System.out.println("Lenght of potential palindrome: " + length + "\n");
//Validate input string and determine whether this is a palindrome
pal.isPal(palindrome, length);
if(unequal == false)
System.out.println("It is a palindrome. ");
else
System.out.println("It is not a palindrome.");
}//end main()
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