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:
public static string Encode(string toEncode)
{
StringBuilder sb = new StringBuilder();
int count = 1;
char current = toEncode[0];
for (int i = 1; i < toEncode.Length; i++)
{
if (current == toEncode[i])
{
count++;
} else
{
sb.AppendFormat("{0}{1}", count, current);
count = 1;
current = toEncode[i];
}
}
sb.AppendFormat("{0}{1}", count, current);
return sb.ToString();
}Note that RLE is a primitive form of compression and should probably be avoided. If you need to compress something for transmission or storage you might be better off using something like GZipStream.