Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases. For example, "A man, a plan, a canal: Panama" is a palindrome. "race a car" is not a palindrome.

isPalindrome.java

public class Solution {
    public boolean isPalindrome(String s) {
        // Start typing your Java solution below
        // DO NOT write main() function
        int size = s.length();
        String lcs = s.toLowerCase();
        int left = 0;
        int right = size - 1;
        while(right >= left) {
            if(lcs.charAt(right) == lcs.charAt(left)) {
                right--;
                left++;
            } else if(!Character.isLetter(lcs.charAt(right))) {
                right--;
            } else if(!Character.isLetter(lcs.charAt(left))) {
                left++;
            } else {
                return false;
            }
        }
        
        return true;
    }

}

This case will fails for numbers

public int isPalindrome(String A) {

    int size = A.length();
    String lcs = A.toLowerCase();
    int left = 0;
    int right = size - 1;
    while(right >= left) {
        boolean isDigitComp = (Character.isDigit(lcs.charAt(right)) && Character.isDigit(lcs.charAt(left)))
        && (Integer.parseInt(String.valueOf(lcs.charAt(right))) == Integer.parseInt(String.valueOf(lcs.charAt(left))));
        
        if(isDigitComp || lcs.charAt(right) == lcs.charAt(left)) {
            right--;
            left++;
        } else if(!Character.isDigit(lcs.charAt(right)) && !Character.isLetter(lcs.charAt(right))) {
            right--;
        } else if(!Character.isDigit(lcs.charAt(left)) && !Character.isLetter(lcs.charAt(left))) {
            left++;
        } else {
            return 0;
        }
    }
    
    return 1;
}

import re
class Palindrome:
    # @param A : string
    # @return an integer
    def isPalindrome(self, A):
        if A == "":
            return 1

        A = re.sub('[^a-zA-Z0-9]', '', A)

        if A == "":
            return 1

        A = A.lower()

        i = 0
        j = len(A) - 1
        while i < j:
            if A[i] != A[j]:
                return 0
            i += 1
            j -= 1
        return 1

public static int isPalindrome(String A) {
if(A == null )
{
return 0;
}
A = removeSplChar(A);
System.out.println("After remove char: "+A);
if( A.length() == 0 || A.length() == 1)
{
return 1;
}

	boolean ispalindrome = true;
	A=A.toLowerCase();
	for(int i = 0,j=A.length()-1 ; i<A.length() ; i++,j--)
	{
		if(A.charAt(i) != A.charAt(j))
		{		
			ispalindrome = false;
			break;
		}
	}
	if(ispalindrome)
    {
		return 1;
    }
	return 0;
}
private static String removeSplChar(String A) {
	String x = "";
	for(int i = 0 ; i<A.length() ; i++)
	{
		int a = A.charAt(i);
		if(a>= 65 && a<= 90)
		{
			x = x+A.charAt(i);
			
		}
		
		if(a>= 97 && a<= 122)
		{
			x = x+A.charAt(i);
			
		}
		if(a>= 48 && a<= 57)
		{
			x = x+A.charAt(i);
			
		}
	}
	return x;
}