C# Online Compiler | .NET Fiddle

// This is a solution to a question that was asked as part of:
// https://www.devleader.ca/2023/09/02/tons-of-beginner-resources-dev-leader-weekly-7/

using System;

bool IsPalindrome(string input)
{
    if (string.IsNullOrWhiteSpace(input))
	{
		return false;
	}

    // Create a Span from the input string
    var inputSpan = input.AsSpan();
    
    // Pointers to the start and end of the span
    int left = 0, right = inputSpan.Length - 1;

    while (left < right)
    {
        // Skip non-alphanumeric characters from the left
        while (left < right && !char.IsLetterOrDigit(inputSpan[left]))
            left++;

        // Skip non-alphanumeric characters from the right
        while (left < right && !char.IsLetterOrDigit(inputSpan[right]))
            right--;

        // If characters do not match (case insensitive), then it's not a palindrome
        if (char.ToLowerInvariant(inputSpan[left]) != char.ToLowerInvariant(inputSpan[right]))
            return false;

        left++;
        right--;
    }

    return true;
}

void Test(string input)
{
	Console.WriteLine($"{input}: {IsPalindrome(input)}");
}

Test("hello world");
Test(null);
Test("");
Test("    ");
Test("race car");
Test("racecar");
Test("RaCeCaR");
Test("1");
Test("11");
Test("111");

 
// This is a solution to a question that was asked as part of:
// https://www.devleader.ca/2023/09/02/tons-of-beginner-resources-dev-leader-weekly-7/
​
using System;
​
bool IsPalindrome(string input)
{
    if (string.IsNullOrWhiteSpace(input))
    {
        return false;
    }
​
    // Create a Span from the input string
    var inputSpan = input.AsSpan();
    
    // Pointers to the start and end of the span
    int left = 0, right = inputSpan.Length - 1;
​
    while (left < right)
    {
        // Skip non-alphanumeric characters from the left
        while (left < right && !char.IsLetterOrDigit(inputSpan[left]))
            left++;
​