51 lines
1.4 KiB
Java
51 lines
1.4 KiB
Java
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;
|
|
}
|
|
}
|