using System;

using System.Linq;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        Console

            .WriteLine(

                SeparateByCamelCase("TestString") == "Test String" // True

            );

    }

    public static string SeparateByCamelCase(string str)

    {

        return String.Join(" ", SplitByCamelCase(str));

    }

    public static IEnumerable<string> SplitByCamelCase(string str) 

    {

        if (str.Length == 0) 

            return new List<string>();

        return 

            new List<string> 

            { 

                Head(str) 

            }

            .Concat(

                SplitByCamelCase(

                    Tail(str)

                )

            );

    }

    public static string Head(string str)

    {

        return new String(

                    str

                        .Take(1)

                        .Concat(

                            str

                                .Skip(1)

                                .TakeWhile(IsLower)

                        )

                        .ToArray()

                );

    }

    public static string Tail(string str)

    {

        return new String(

                    str

                        .Skip(

                            Head(str).Length

                        )

                        .ToArray()

                );

    }

    public static bool IsLower(char ch) 

    {

        return ch >= 'a' && ch <= 'z';

    }

}