using System;

public class Program

{

    public static void Main()

    {

        FindString findDistance = new FindString();

        bool result = findDistance.checkDistance("cordova", 'c', 'a', 6);

        Console.WriteLine("Function returned: " + result);

    }

}

​

​

public class FindString

    {

        public bool checkDistance(string word, char a, char b, int distance) {

            var firstIndexA = word.IndexOf(a);

            var firstIndexB = word.IndexOf(b);

​

            if (firstIndexA == -1 || firstIndexB == -1)

                return false;

​

            int index = firstIndexA;

            char splitStr = a;

            char findStr = b;

​

            if (firstIndexA > firstIndexB) {

                index = firstIndexB;

                findStr = a;

                splitStr = b;

            }

​

​

            int posA = 0;

            do {

                word = word.Substring(index + 1);

                int posB = word.IndexOf(findStr);

                if (posB >= 0 && posB <= distance - 1)

                    return true;

                if (word.Length < distance)

                    return false;

                posA = word.IndexOf(splitStr);

            }

            while (posA >= 0);

            return false;

        }

    }