using System;

public class Program

{

    static int large_substring(string str)

    {

        if (string.IsNullOrEmpty(str))

            return 0;

​

        const int Chars = 256;

​

        int CurrentCountChars = 1;

        int MaxCountChars = 1;

​

        int PreviousIndex;

​

        int[] visited = new int[Chars];

​

        for (int i = 0; i < Chars; i++)

        {

            visited[i] = -1;

        }

​

        visited[str[0]] = 0;

​

        for (int i = 1; i < str.Length; i++)

        {

            PreviousIndex = visited[str[i]];

​

            if (PreviousIndex == -1 || i - CurrentCountChars > PreviousIndex)

            {

                CurrentCountChars++;

            }

            else

            {

                if (CurrentCountChars > MaxCountChars)

                    MaxCountChars = CurrentCountChars;

​

                CurrentCountChars = i - PreviousIndex;

            }

​

            visited[str[i]] = i;

        }

​

        if (CurrentCountChars > MaxCountChars)

            MaxCountChars = CurrentCountChars;

​

        return MaxCountChars;

    }

​

​

    public static void Main()

    {

​

        if (large_substring("afsdffsd") == 4)

        {

            Console.WriteLine("Тест 1 пройден");

        }

​

        if (large_substring("") == 0)

        {

            Console.WriteLine("Тест 2 пройден");

        }

​

        if (large_substring("ffffffffffff") == 1)

        {

            Console.WriteLine("Тест 3 пройден");

        }

​

        if (large_substring("abcdefghijklmnopqrstuvwxyz") == 26)

        {

            Console.WriteLine("Тест 4 пройден");

        }

​

        if (large_substring("afsdffsdQPODDDD") == 7)

        {

            Console.WriteLine("Тест 5 пройден");

        }

​

    }

}