using System;

using System.Linq;

using System.Diagnostics;

public class Program

{

    // This program shows that using bit arithmetic is faster than using Linq to search an array when deciding if a character is a vowel.

    public static void Main()

    {

        var trials = 100000;

        var letters = new char[] { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z' };

        var timer = new Stopwatch();

        timer.Start();

        for(var i = 0; i < trials; i++)

        {

            char c = letters[i%26];

            IsVowelLinq(c);

        }

        timer.Stop();

        Console.WriteLine("Time for LINQ      = " + timer.ElapsedMilliseconds + " msec");

        timer.Reset();

        timer.Start();

        for(var i = 0; i < trials; i++)

        {

            char c = letters[i%26];

            IsVowelBitArithmetic(c);

        }

        timer.Stop();

        Console.WriteLine("Time for Bit masks = " + timer.ElapsedMilliseconds + " msec");

        Console.WriteLine("Done");

    }

    public static bool IsVowelLinq(char c)

    {

        char[] vowels = new[] { 'a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U' };

        return vowels.Any(ch => ch == c);

    }

    private static int VowelMask = (1 << 1) | (1 << 5) | (1 << 9) | (1 << 15) | (1 << 21);

    public static bool IsVowelBitArithmetic(char c)

    {

        // The OR with 0x20 lowercases the letters

        // The test c > 64 rules out punctuation, digits, and control characters.

        // An additional test would be required to eliminate characters above ASCII 127.

        return (c > 64) && ((VowelMask &  (1 << ((c | 0x20) % 32))) != 0);

    }

}