Palindrome Checker

using System;
using System.Text.RegularExpressions;

public class PalindromeChecker
{
    /// <summary>
    /// Checks if a string is a palindrome (ignoring case, spaces, and punctuation)
    /// </summary>
    /// <param name="input">String to check</param>
    /// <returns>True if palindrome, false otherwise</returns>
    public static bool IsPalindrome(string input)
    {
        if (string.IsNullOrEmpty(input))
            return true;
        
        // Remove non-alphanumeric characters and convert to lowercase
        string cleaned = Regex.Replace(input.ToLower(), @"[^a-z0-9]", "");
        
        int left = 0;
        int right = cleaned.Length - 1;
        
        while (left < right)
        {
            if (cleaned[left] != cleaned[right])
                return false;
            
            left++;
            right--;
        }
        
        return true;
    }
    
    public static void Main()
    {
        string[] testCases = {
            "A man a plan a canal Panama",
            "race a car",
            "Was it a car or a cat I saw?",
            "Madam",
            "hello"
        };
        
        foreach (string test in testCases)
        {
            bool result = IsPalindrome(test);
            Console.WriteLine($"'{test}' -> {(result ? "Palindrome" : "Not a palindrome")}");
        }
    }
}