package Others;

class Palindrome {

 private String reverseString(String x) { // *helper method
 StringBuilder output = new StringBuilder(x);
 return output.reverse().toString();
 }

 public boolean FirstWay(String x) { // *palindrome method, returns true if palindrome
 if (x == null || x.length() <= 1)
 return true;
 return x.equalsIgnoreCase(reverseString(x));
 }

 public boolean SecondWay(String x) {
 if (x.length() == 0 || x.length() == 1)
 return true;

 if (x.charAt(0) != x.charAt(x.length() - 1))
 return false;

 return SecondWay(x.substring(1, x.length() - 1));
 }

 /**
 * This method ignores all non-alphanumeric characters and case runs in O(n)
 * where n is the length of s
 * 
 * @param s String to check
 * @return true if s is palindrome else false
 */
 public boolean isPalindrome(String s) {
 s = s.toLowerCase().trim();
 StringBuilder sb = new StringBuilder();
 for (char c : s.toCharArray()) {
 if (Character.isLetter(c) || Character.isDigit(c))
 sb.append(c);
 }
 s = sb.toString();
 int start = 0;
 int end = s.length() - 1;
 while (start <= end) {
 if (s.charAt(start++) != s.charAt(end--))
 return false;

 }
 return true;
 }
}