Run-Length Encoding (RLE) in C#

Fri, 17 Aug 2012 14:47:10 -0400

I recently came across a file format that required usage of Run Length Encoding to handle. This involved writing methods for both decoding and encoding. Here are my results:

To decode, you just use a string and concatenate it with each numeric character that is encountered until you hit a non-numeric character. You use this string to figure out how many times you need to repeat the character:

public static string Decode(string toDecode)
{
    string coefficient = String.Empty;
    StringBuilder sb = new StringBuilder();

    foreach (char current in toDecode)
    {
        if (char.IsDigit(current))
            coefficient += current;
        else
        {
            if (coefficient == String.Empty)
                sb.Append(current);
            else
            {
                int count = int.Parse(coefficient);
                coefficient = String.Empty;
                for (int j = 0; j < count; j++)
                    sb.Append(current);
            }
        }
    }
    return sb.ToString();
}

Similarly, for encoding. I used a stringbuilder and a counter to figure out how many times a character was repeated then appended this to the stringbuilder:

Compression on bradleycarey.com

Run-Length Encoding (RLE) in C#