using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {   

        String searchTerm = "banG";

        CitySearch.CityFinder myFinder = new CitySearch.CityFinder();

        CitySearch.ICityResult myResults = myFinder.Search(searchTerm);

        Console.WriteLine("Search Results for: `" + searchTerm + "`");

        Console.WriteLine("\nNextCities Result:" + myResults.NextCities.Count);

​

        foreach (string cityName in  myResults.NextCities) {

            Console.WriteLine("`" + cityName + "`");

        }

        Console.WriteLine("\nNextLetters Result:" + myResults.NextLetters.Count);

        foreach (string letter in  myResults.NextLetters) {

            Console.WriteLine("`" + letter + "`");

        }

    }

}

​

namespace CitySearch

{

    using System.Collections.Generic;

​

    public interface ICityResult

    {

        ICollection<string> NextLetters { get; set; }

        ICollection<string> NextCities { get; set; }

    }

    public class CityResult : ICityResult

    {

        public ICollection<string> NextLetters { get; set; }

        public ICollection<string> NextCities { get; set; }

        public CityResult() {

            NextLetters = new HashSet<String>();

            NextCities = new HashSet<String>();

        }

    }

    public interface ICityFinder

    {

        ICityResult Search(string searchString);

    }

    public class CityFinder : ICityFinder 

    {           

        string[] testData = {

            "LAGOS", 

            "LA PAZ", 

            "LA PLATA",

            "LA-EPLATA",

            "LEEDS",

            "BANDUNG",

            "BANGUI",

            "BANGKOK",

            "BANGKOK",

            "BANGALORE",

            "ZARIA",

            "ZHUGHAI",

            "ZIBO"          

        };

        HashSet<String> sourceData;

        public CityFinder() {

            // initialize source data

            sourceData = new HashSet<String>(testData);

        }

        public ICityResult Search(string searchString)

        {

            // normalize search string to lowercase

            String searchStringNormalized = searchString.ToLower();

            int nexCharPosition = searchString.Length;

            CitySearch.ICityResult searchResults = new CitySearch.CityResult();

            foreach (string cityName in sourceData)

            {

                // normalize data to lowercase

                if (cityName.ToLower().StartsWith(searchStringNormalized)) {

                   // add to city results

                   searchResults.NextCities.Add(cityName);

                   searchResults.NextLetters.Add(cityName[nexCharPosition].ToString());

                }

            }

            return searchResults;

        }

    }

}