/// <summary>
/// Implement the reply() method so it returns the message "hello world"
/// </summary>
/// <returns>the greeting to the world</returns>
String reply();

Any number divisible by three is replaced by the word fizz and any divisible by five by the word buzz. Numbers divisible by both become fizzbuzz. A player who makes a mistake has to take a drink.
Einstein will choose a random number to start with – for example: 4, buzz, fizz, 7, 8, fizz, buzz, 11, fizz, 13, 14, fizzbuzz…

String answer (int number);

C#

using System;

public class MyKata
{
    /// <summary>
    /// Welcome a guest
    ///
    /// -Jane Austen is a women, so say Hello Ms. Austen
    /// -George Orwell is a man, so say Hello Mr. Orwell
    /// -Isaac Newton was knighted, so say Hello Sir Newton
    /// </summary>
    /// <param name="lastname">the last name of the guest</param>
    /// <param name="isWoman">true if the guest is female</param>
    /// <param name="isSir">true if the guest was knighted by the queen</param>
    /// <returns>issues welcome text to the guest</returns>
    public string welcome(string lastname, bool isWoman, bool isSir)
    {
        var title = "Mr.";

        if (isWoman)
            title = "Ms.";
        else if (isSir)
            title = "Sir";

        return String.Format("Hello {0} {1}", title, lastname);
    }
}

public class NASACountDown
{
    public int[] countdown(int start)
    {
        var count = new int[start + 1];

        for (var i = 0; i <= start; i++)
        {
            count[i] = start - i;
        }

        return count;
    }
}

C#

public class MyKata
{
    /// <summary>
    /// Calcular el 'máximo común divisor'
    /// http://es.wikipedia.org/wiki/Algoritmo_de_Euclides
    /// </summary>
    /// <param name="number1">el primer número ('numerador')</param>
    /// <param name="number2">el segundo número ('denominador')</param>
    /// <returns>mcd de number1 y number2</returns>
    public int calcGCD(int number1, int number2)
    {
        return number2 == 0 ? number1 : calcGCD(number2, number1 % number2);
    }
}

C#

using System;
using System.Text.RegularExpressions;

public class MyKata
{
    /// <summary>
    /// Traduce un texto coloquial a un texto compatible con las noticias de TV
    /// </summary>
    /// <param name="text">cadena completa de slang (p.e. 'I am $kewl$.')</param>
    /// <param name="dictionary">diccionario de slang - en parejas, como {{slang, non-slang}, ...}</param>
    /// <returns>el texto 'limpio'</returns>
    public string translate(string text, string[][] dictionary)
    {
        const string pat = @"[$][\w|\s]+[$]";

        var occurrences = new Regex(pat).Matches(text);

        foreach (var match in occurrences)
        {
            var word = match.ToString().Replace("$", string.Empty);
            var index = Array.FindIndex(dictionary, e => e[0].Equals(word));
            text = text.Replace(match.ToString(), dictionary[index][1]);
        }

        return text;
    }
}

C#

using System.Collections.Generic;

public class MyKata
{
    /// <summary>
    /// Convert an Arabic numeral to Roman numeral
    /// </summary>
    /// <param name="number">an Arabic numeral</param>
    /// <returns>the Roman numeral equivalent to the Arabic numeral</returns>
    public string convert(int number)
    {
        var result = string.Empty;

        var numeral = new SortedList<int, string>()
                            {
                                { 50, "L"  },
                                { 40, "XL" },
                                { 10, "X"  },
                                {  9, "IX" },
                                {  5, "V"  },
                                {  4, "IV" },
                                {  1, "I"  }
                            };

        var i = numeral.Count - 1;

        while (number > 0)
        {
            var arabic = numeral.Keys[i];

            while (arabic <= number)
            {
                result += numeral.Values[i];
                number -= arabic;
            }
            i--;
        }

        return result;
    }
}

C#

using System.Linq;

public class MyKata
{
    public bool containsPrimeNumber(string code1, string code2, string code3)
    {
        return isSumPrime(code1) || isSumPrime(code2) || isSumPrime(code3);
    }

    private static bool isSumPrime(string code)
    {
        var n = code.ToCharArray().Sum(c => int.Parse(c.ToString()));

        int i;

        for (i = 2; i < n; i++)
            if (n % i == 0)
                return false;

        return i == n;
    }
}

C#

using System.Collections.Generic;
using System.Linq;

public class MyKata
{
    public enum Day { SUN, MON, TUE, WED, THU, FRI, SAT }

    private class Ticket
    {
        public int Age { get; set; }
        public bool IsStudent { get; set; }
    }

    private int _runtime;
    private Day _day;
    private bool _isParquet;
    private bool _is3D;
    private List<Ticket> _tickets;

    /// <summary>
    /// (1) New customers arrive at your ticket booth and tell you
    /// what movie they'd like to see (so keep it in mind 
    /// </summary>
    /// <param name="runtime">movie's runtime in minutes</param>
    /// <param name="day">day of the week (enum)</param>
    /// <param name="isParquet">true if seating category is 'parquet' (and not 'loge')</param>
    /// <param name="is3D">true if the movie's shown in 3D</param>
    public void startPurchase(int runtime, Day day, bool isParquet, bool is3D)
    {
        _tickets = new List<Ticket>();
        _runtime = runtime;
        _day = day;
        _isParquet = isParquet;
        _is3D = is3D;

    }

    /// <summary>
    /// (2) Add a ticket to the customers' bill
    /// </summary>
    /// <param name="age">the age of the ticket buyer in years</param>
    /// <param name="isStudent">true if the ticket buyer is a student</param>
    public void addTicket(int age, bool isStudent)
    {
        _tickets.Add(new Ticket { Age = age, IsStudent = isStudent});
    }

    /// <summary>
    /// (3) Calculate the total admission for the current customer(s)
    /// </summary>
    /// <returns>total in dollars</returns>
    public float finishPurchase()
    {
        var numTickets = _tickets.Count;

        var basic = _tickets.Sum(t => t.Age < 13 ? 5.5f : (t.Age >= 65 || numTickets >= 20) ? 6f : (t.IsStudent ? 8f : 11f));

        var exceptions = 0f;

        if (_is3D) exceptions += 3f;
        if (_runtime>120) exceptions += 1.5f;
        if (_day == Day.THU && _tickets.Count<20) exceptions -= 2.0f;
        if (_day == Day.SAT || _day == Day.SUN) exceptions += 1.5f;
        if (!_isParquet) exceptions += 1.5f;

        exceptions *= numTickets;

        return basic + exceptions;
    }
}

C#

using System;
using System.Linq;

public class Books
{
    /// <summary>
    /// Calculate the ISBN-13 check digit
    /// </summary>
    /// <param name="isbn">an incomplete ISBN code (12 characters, no hyphens)</param>
    /// <returns>code's check digit</returns>
    public int calcCheckDigit(String isbn)
    {
        var i = 0;
        return (10 - isbn.Sum(c => int.Parse(c.ToString()) * (i++ % 2 == 0 ? 3 : 1)) % 10) % 10;
    }
}

C#

using System.Collections.Generic;

public class trainchaos
{
    Stack<int> stack = new Stack<int>();

    /// <summary>
    /// Adds a car to the siding
    /// </summary>
    /// <param name="car"> a train car (represented by a number)</param>
    public void push(int car)
    {
        stack.Push(car);
    }

    /// <summary>
    /// Removes a car from the siding
    /// </summary>
    /// <returns>a train car (number), -1 if stack is empty</returns>
    public int pop()
    {
        return stack.Count > 0 ? stack.Pop() : -1;
    }

    /// <summary>
    ///  Return the current front car (number) without removing it
    /// </summary>
    /// <returns> a train car (number), -1 if stack is empty</returns>
    public int peek()
    {
        return stack.Count > 0 ? stack.Peek() : -1;
    }
}

C#

using System;

public class HappyNumbers
{
  /// <summary>
  /// Comprueba si un número es un 'número feliz'
  /// </summary>
  /// <param name="number">número a comprobar</param>
  /// <returns>true si el parámetro es un número feliz</returns>
  private bool isHappy(long p)
  {
     if (p < 10)
     {
         return p == 1 || p == 7;
     }
     long sum = 0;
     var number = p.ToString();

     foreach (var digit in number)
     {
         var c = digit - '0';
         sum = sum + c*c;
     }
     return isHappy(sum);
  }
}