| Methods Summary |
|---|
| public static java.math.BigInteger | findPalindrome(java.math.BigInteger num)find a palindromic number given a starting point, by
calling ourself until we get a number that is palindromic.
if (num.compareTo(BigInteger.ZERO) < 0)
throw new IllegalStateException("negative");
if (isPalindrome(num))
return num;
if (verbose)
System.out.println("Trying " + num);
return findPalindrome(num.add(reverseNumber(num)));
|
| public static boolean | isPalindrome(java.math.BigInteger num)Check if a number is palindromic.
String digits = num.toString();
int numDigits = digits.length();
if (numDigits >= MAX_DIGITS) {
throw new IllegalStateException("too big");
}
// Consider any single digit to be as palindromic as can be
if (numDigits == 1)
return true;
for (int i=0; i<numDigits/2; i++) {
// System.out.println(
// digits.charAt(i) + " ? " + digits.charAt(numDigits - i - 1));
if (digits.charAt(i) != digits.charAt(numDigits - i - 1))
return false;
}
return true;
|
| public static void | main(java.lang.String[] argv)
for (int i=0; i<argv.length; i++)
try {
BigInteger l = new BigInteger(argv[i]);
if (l.compareTo(BigInteger.ZERO) < 0) {
System.err.println(argv[i] + " -> TOO SMALL");
continue;
}
System.out.println(argv[i] + "->" + findPalindrome(l));
} catch (NumberFormatException e) {
System.err.println(argv[i] + "-> INVALID");
} catch (IllegalStateException e) {
System.err.println(argv[i] + "-> " + e);
}
|
| static java.math.BigInteger | reverseNumber(java.math.BigInteger num)
String digits = num.toString();
int numDigits = digits.length();
char[] sb = new char[numDigits];
for (int i=0; i<digits.length(); i++) {
sb[i] = digits.charAt(numDigits - i - 1);
}
// Debug.println("rev",
// "reverseNumber(" + digits + ") -> " + "\"" + sb + "\"");
return new BigInteger(new String(sb));
|
