using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Security.Cryptography;

​

public static class Program

{

    public static void Main()  

    {

        Console.WriteLine("This christmas tree should really be three times taller...");

​

        var sapling = new List<List<int>>

        {

            new List<int> { 1 },

            new List<int> { 1, 1 },

            new List<int> { 1, 2, 1 },

            new List<int> { 1, 3, 3, 1 },

            new List<int> { 1, 4, 6, 4, 1 }

        };

        var tree = GrowTree(sapling, height: 5); // So this should be three times higher?

        PrintChristmasTree(tree);

        var sum = tree.Select(row => row.Sum()).Sum();

        var answer = sum.ToString();

        if (IsCorrect(answer))

        {

            Console.WriteLine("A nice tall tree! {0} is the correct answer.", answer);

        }

        else if (IsCorrect(tree.Count))

        {

            Console.WriteLine("Seems tall enough, but looks kinda funny...");

        }

        else

        {

            Console.WriteLine("Still to short :-/");

        }

    }

    static List<List<int>> GrowTree(List<List<int>> sapling, int height)

    {

        if (sapling.Count >= height)

        {

            return sapling;

        }

        var bottomRow = sapling.Last();

        // Console.WriteLine("Bottom row: {0}", string.Join("~", bottomRow));

        var newRow = new List<int>();

        newRow.Add(1);

        for (int i = 0; i < bottomRow.Count - 1; i++)

        {

            var number = 7; // Maybe 7 isn't good enough?

            newRow.Add(number);

        }

        newRow.Add(1);

        // Console.WriteLine("New row: {0}", string.Join("~", newRow));

        sapling.Add(newRow);

        return GrowTree(sapling, height);

    }

    static void PrintChristmasTree(List<List<int>> tree)

    {

        Console.Write('\u2605');

        Console.WriteLine();

        foreach (List<int> row in tree)

        {

            Console.WriteLine(string.Join("~", row));

        }

    }

​

    static bool IsCorrect(string answer)

    {

        var correctBytes = new byte[] { 0xD8, 0x44, 0x2B, 0xAF, 0x6F, 0x43, 0x7F, 0x1F, 0x68, 0x2F, 0x0C, 0xAE, 0x9D, 0xDE, 0x1A, 0xF2, 0xD3, 0xC5, 0x95, 0xD8, 0x8A, 0x36, 0x97, 0x18, 0x81, 0xD3, 0x6B, 0x30, 0x47, 0x85, 0xD0, 0x1C };

        using (SHA256 sha256Hash = SHA256.Create())

        {

            var bytes = sha256Hash.ComputeHash(Encoding.UTF8.GetBytes(answer));

​

            return bytes.SequenceEqual(correctBytes);

        }

    }

    static bool IsCorrect(int answer)

    {

        var correctBytes = new byte[] { 0xE6, 0x29, 0xFA, 0x65, 0x98, 0xD7, 0x32, 0x76, 0x8F, 0x7C, 0x72, 0x6B, 0x4B, 0x62, 0x12, 0x85, 0xF9, 0xC3, 0xB8, 0x53, 0x03, 0x90, 0x0A, 0xA9, 0x12, 0x01, 0x7D, 0xB7, 0x61, 0x7D, 0x8B, 0xDB };

        using (SHA256 sha256Hash = SHA256.Create())

        {

            var bytes = sha256Hash.ComputeHash(Encoding.UTF8.GetBytes(answer.ToString()));

​

            return bytes.SequenceEqual(correctBytes);

        }

    }

}