For Reddit Easy Challenge 275

Splurthian_Chemistry_101.cs

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

namespace Splurthian_Chemistry_101
{
    class Program
    {
        static Tuple<string, string>[] isValidInputs =
        {
            new Tuple<string, string>("Spenglerium", "Ee"),
            new Tuple<string, string>("Zeddemorium", "Zr"),
            new Tuple<string, string>("Venkmine", "Kn"),
            new Tuple<string, string>("Stantzon", "Zt"),
            new Tuple<string, string>("Melintzum", "Nn"),
            new Tuple<string, string>("Tullium", "Ty")
        };

        static string[] makeSymbolsInputs = new string[]
        {
            "Gozerium",
            "Slimyrine"
        };

        static string[] countSymbolsInput = new string[]
        {
            "Zuulon",
            "Xenon"
        };

        static void Main(string[] args)
        {
            foreach(var input in isValidInputs)
                Console.WriteLine(input.Item1 + ", " + input.Item2 + " -> " + IsValid(input.Item1, input.Item2));

            Console.ReadKey();
            Console.Clear();

            foreach (var input in makeSymbolsInputs)
                Console.WriteLine(input + " -> " + MakeSymbol(input));

            Console.ReadKey();
            Console.Clear();

            foreach (var input in countSymbolsInput)
                Console.WriteLine(input + " -> " + CountValidSymbols(input));

            Console.ReadKey();
            Console.Clear();

            foreach (var input in countSymbolsInput)
                Console.WriteLine(input + " -> " + CountValidSymbolsNoRules(input));

            Console.ReadKey();
        }

        /// <summary>
        /// Determines if the passed in 
        /// symbol is valid for the passed in element
        /// </summary>
        /// <param name="element">
        /// Element to be validated against
        /// </param>
        /// <param name="symbol">
        /// Symbol to validate
        /// </param>
        static bool IsValid(string element, string symbol)
        {
            element = element.ToUpper();
            symbol = symbol.ToUpper();

            if (symbol.Length != 2)
                return false;

            foreach(var c in symbol)
            {
                int loc = element.IndexOf(c);
                if (loc == -1)
                    return false;

                element = element.Substring(loc + 1);
            }

            return true;
        }

        /// <summary>
        /// Creates the most alphabetic symbol 
        /// possible for the passed in element
        /// </summary>
        /// <param name="element">
        /// Element to create a symbol for
        /// </param>
        static string MakeSymbol(string element)
        {
            element = element.ToUpper();
            string symbol = "";
            string substring = element.Substring(0, element.Length - 1);

            symbol += substring.OrderBy(x => x).Take(1).Single();
            substring = element.Substring(element.IndexOf(symbol) + 1);

            symbol += substring.OrderBy(x => x).Take(1).Single();
            symbol = symbol[0] + symbol[1].ToString().ToLower();
            return symbol;
        }

        /// <summary>
        /// Returns the amount of valid element symbols
        /// </summary>
        /// <param name="element">
        /// Element to count symbols
        /// </param>
        static int CountValidSymbols(string element)
        {
            element = element.ToUpper();
            List<string> symbols = new List<string>();

            for (int i = 0; i < element.Length - 1; i++)
                for (int j = i + 1; j < element.Length; j++)
                    symbols.Add(element[i].ToString() + element[j].ToString());

            return symbols.Distinct().ToArray().Length;
        }

        /// <summary>
        /// Returns the amount of valid element symbols
        /// This method does not take into account max or min symbol length
        /// </summary>
        /// <param name="element">
        /// Element to count symbols
        /// </param>
        static int CountValidSymbolsNoRules(string element)
        {
            List<string> symbols = new List<string>();

            foreach(var s in CountValidSymbolsNoRulesWorker("", element))
                symbols.Add(s.ToUpper());

            return symbols.Distinct().ToArray().Length;
        }

        /// <summary>
        /// Recursive function used to determine every possible output
        /// </summary>
        /// <param name="pre">
        /// The prefix of this symbol (Should start with "")
        /// </param>
        /// <param name="parse">
        /// Every other letter of this symbol (should start with the entire element name)
        /// </param>
        static IEnumerable<string> CountValidSymbolsNoRulesWorker(string pre, string parse)
        {
            for(int i = 0; i < parse.Length; i++)
            {
                yield return pre + parse[i];

                foreach(var s in CountValidSymbolsNoRulesWorker(pre + parse[i], parse.Substring(i + 1)))
                    yield return s;
            }
        }
    }
}

For Reddit Easy Challenge 275