using System;

public class Program

{

    public bool haveUnique(String str)

{

    bool[] charSet = new bool[256];

​

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

    {

        int theValue = str[i];

        if (charSet[theValue])

        return false;

        charSet[theValue] = true;

    }

​

    return true;

}

    public static void Main()

    {

        Program p=new Program();

        bool p1=p.haveUnique("apple");

        Console.WriteLine("{0}",p1);

    }

}