using System;

public class GFG

{

    public static void Reverse(string str)

    {

        char[] c = str.ToCharArray();

        int left = 0;

        int right = c.Length - 1;

​

        while (left < right)

        {

            // Skip over special characters (non-alphanumeric)

            if (!((c[left] >= 'a' && c[left] <= 'z') || (c[left] >= 'A' && c[left] <= 'Z')))

            {

                left++;

               continue;

            }

            if (!((c[right] >= 'a' && c[right] <= 'z') || (c[right] >= 'A' && c[right] <= 'Z')))

            {

                right--;

                continue;

            }

            // Swap characters

            char temp = c[left];

            c[left] = c[right];

            c[right] = temp;

​

            left++;

            right--;

        }

        Console.WriteLine(new string(c));

    }

    public static void Main(string[] args)

    {

      //  string str = "C#$1sh@rp";

        string str = "He%$llo";

​

        Reverse(str);

    }

}

​