Find Unique Characters in a File

Question

I have a file with 450,000+ rows of entries. Each entry is about 7 characters in length. What I want to know is the unique characters of this file.

For instance, if my f

Answer 1

Where C:/data.txt contains 454,863 rows of seven random alphabetic characters, the following code

using System;
using System.IO;
using System.Collections;
using System.Diagnostics;

namespace ConsoleApplication {
    class Program {
        static void Main(string[] args) {
            FileInfo fileInfo = new FileInfo(@"C:/data.txt");
            Console.WriteLine(fileInfo.Length);

            Stopwatch sw = new Stopwatch();
            sw.Start();

            Hashtable table = new Hashtable();

            StreamReader sr = new StreamReader(@"C:/data.txt");
            while (!sr.EndOfStream) {
                char c = Char.ToLower((char)sr.Read());
                if (!table.Contains(c)) {
                    table.Add(c, null);
                }
            }
            sr.Close();

            foreach (char c in table.Keys) {
                Console.Write(c);
            }
            Console.WriteLine();

            sw.Stop();
            Console.WriteLine(sw.ElapsedMilliseconds);
        }
    }
}

produces output

4093767
mytojevqlgbxsnidhzupkfawr
c
889
Press any key to continue . . .

The first line of output tells you the number of bytes in C:/data.txt (454,863 * (7 + 2) = 4,093,767 bytes). The next two lines of output are the unique characters in C:/data.txt (including a newline). The last line of output tells you the number of milliseconds the code took to execute on a 2.80 GHz Pentium 4.