对文本文件中的字符进行计数/排序

Question

I am trying to write a program that reads a text file, sorts it by character, and keeps track of how many times each character appears in the document. This is what I have so far.

class Program
{
    static void Main(string[] args)
    {
        CharFrequency[] Charfreq = new CharFrequency[128];

        try
        {            
        string line;
        System.IO.StreamReader file = new System.IO.StreamReader(@"C:\Users\User\Documents\Visual Studio 2013\Projects\Array_Project\wap.txt");
        while ((line = file.ReadLine()) != null)
        {
            int ch = file.Read();

            if (Charfreq.Contains(ch))
            {

            }     
        }

        file.Close();

        Console.ReadLine();
        }
        catch (Exception e)
        {
            Console.WriteLine("The process failed: {0}", e.ToString());
        }
    }
}

My question is, what should go in the if statement here?

I also have a Charfrequency class, which I'll include here in case it is helpful/necessary that I include it (and yes, it is necessary that I use an array versus a list or arraylist).

public class CharFrequency
{
    private char m_character;
    private long m_count;

    public CharFrequency(char ch)
    {
        Character = ch;
        Count = 0;
    }

    public CharFrequency(char ch, long charCount)
    {
        Character = ch;
        Count = charCount;
    }

    public char Character
    {
        set
        {
            m_character = value;
        }

        get
        {
            return m_character;
        }
    }

    public long Count
    {
        get
        {
            return m_count;
        }
        set
        {
            if (value < 0)
                value = 0;

            m_count = value;
        }
    }

    public void Increment()
    {
        m_count++;

    }

    public override bool Equals(object obj)
    {
        bool equal = false;
        CharFrequency cf = new CharFrequency('\0', 0);

        cf = (CharFrequency)obj;

        if (this.Character == cf.Character)
            equal = true;

        return equal;
    }

    public override int GetHashCode()
    {
        return m_character.GetHashCode();
    }

    public override string ToString()
    {
        String s = String.Format("'{0}' ({1})     = {2}", m_character, (byte)m_character, m_count);

        return s;
    }

}

Answer 1

Have a look at this post.

https://codereview.stackexchange.com/questions/63872/counting-the-number-of-character-occurrences

It uses LINQ to achieve your goal

Answer 2

You shouldn't use Contains

first you need to initialize your Charfreq array:

CharFrequency[] Charfreq = new CharFrequency[128];

for (int i = 0; i < Charferq.Length; i++)
{
    Charfreq[i] = new CharFrequency((char)i);
}

try

then you can

int ch;

// -1 means that there are no more characters to read,
// otherwise ch is the char read
while ((ch = file.Read()) != -1)
{
     CharFrequency cf = new CharFrequency((char)ch);

     // This works because CharFrequency overloads the
     // Equals method, and the Equals method checks only 
     // for the Character property of CharFrequency
     int ix = Array.IndexOf(Charfreq, cf);

     // if there is the "right" charfrequency
     if (ix != -1)
     {
         Charfreq[ix].Increment();
     }     
}

Note that this isn't the way I would write the program. This is the minimum changes needed to make your program working.

As a sidenote, this program will count the "frequency" of ASCII characters (characters with code <= 127)

CharFrequency cf = new CharFrequency('\0', 0);

cf = (CharFrequency)obj;

And this is an useless initialization:

CharFrequency cf = (CharFrequency)obj;

is enough, otherwise you are creating a CharFrequency just to discard it the line below.

Answer 3

A dictionary is well suited for a task like this. You didn't say which character set and encoding the file was in. So, because Unicode is so common, let's assume the Unicode character set and UTF-8 encoding. (After all, it is the default for .NET, Java, JavaScript, HTML, XML,….) If that's not the case then read the file using the applicable encoding and fix your code because you currently are using UTF-8 in your StreamReader.

Next comes iterating across the "characters". And then incrementing the count for a "character" in the dictionary as it is seen in the text.

Unicode does have a few complex features. One is combining characters, where a base character can be overlaid with diacritics etc. Users view such combinations as one "character", or, as Unicode calls them, graphemes. Thankfully, .NET gives is the StringInfo class that iterates over them as a "text element."

So, if you think about it, using an array would be quite difficult. You'd have to build your own dictionary on top of your array.

The example below uses a Dictionary and is runnable using a LINQPad script . After it creates the dictionary, it orders and dumps it with a nice display.

var path = Path.GetTempFileName();
// Get some text we know is encoded in UTF-8 to simplify the code below
// and contains combining codepoints as a matter of example.
using (var web = new WebClient())
{
    web.DownloadFile("http://superuser.com/questions/52671/which-unicode-characters-do-smilies-like-%D9%A9-%CC%AE%CC%AE%CC%83-%CC%83%DB%B6-consist-of", path); 
}
// since the question asks to analyze a file
var content = File.ReadAllText(path, Encoding.UTF8); 
var frequency = new Dictionary<String, int>();
var itor = System.Globalization.StringInfo.GetTextElementEnumerator(content);
while (itor.MoveNext()) 
{
    var element = (String)itor.Current;
    if (!frequency.ContainsKey(element)) 
    {
        frequency.Add(element, 0);
    }
    frequency[element]++;
}
var histogram = frequency
    .OrderByDescending(f => f.Value)
    // jazz it up with the list of codepoints in each text element
    .Select(pair =>  
        {
            var bytes = Encoding.UTF32.GetBytes(pair.Key);
            var codepoints = new UInt32[bytes.Length/4];
            Buffer.BlockCopy(bytes, 0, codepoints, 0, bytes.Length);
            return new { 
                Count = pair.Value, 
                textElement = pair.Key, 
                codepoints = codepoints.Select(cp => String.Format("U+{0:X4}", cp) ) };
        });
histogram.Dump(); // For use in LINQPad