using System;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine(IsIsogram("ana"));                 //false

        Console.WriteLine(IsIsogram("moose"));               //false

        Console.WriteLine(IsIsogram("moOse"));               //false

        Console.WriteLine(IsIsogram("Dermatoglyphics"));     //true 

        Console.WriteLine(IsIsogram("isogram"));             //true

        Console.WriteLine(IsIsogram("isIsogram"));           //false

        Console.WriteLine(IsIsogram("thumbscrewjapingly"));  //true

        Console.WriteLine(IsIsogram(""));                    //true

    }

    public static bool IsIsogram(string str) 

    {

        // No repeating characters

        // single line solution: str.ToLower().Distinct().Count()==str.Length;

        string initialString = str.ToLower();

        for(int i = 0; i < str.Length; i++)

        {

            if(initialString.Remove(i,1).Contains(initialString[i]))

            {

                return false;

            }

        }

        return true;

    }

}