public static class Exercise
{
    public static string ReverseString(string inputStr)
    {
        var input = new StringBuilder(inputStr);
        var output = new StringBuilder();
        for (var i = inputStr.Length-1; i >= 0; i--)
        {
            output.Append(inputStr[i]);
        }

        return output.ToString();
    }

    public static string ReverseString_InPlace(string inputStr)
    {
        var sb = new StringBuilder(inputStr);
        int i = 0;
        int j = sb.Length-1;
        while (i != j)
        {
            var a = sb[i];
            sb[i] = sb[j];
            sb[j] = a;

            i++;
            j--;
        }

        return sb.ToString();
    }
}