regex/linq to replace consecutive characters with count
I have the following method (written in C#/.NET). Input text consist only of letters (no开发者_JAVA技巧 digits). Returned value is another text in which groups of more than two consecutive characters are replaced with one the character preceded with a count of repetitions. Ex.: aAAbbbcccc -> aAA3b4c
public static string Pack(string text)
{
if (string.IsNullOrEmpty(text)) return text;
StringBuilder sb = new StringBuilder(text.Length);
char prevChar = text[0];
int prevCharCount = 1;
for (int i = 1; i < text.Length; i++)
{
char c = text[i];
if (c == prevChar) prevCharCount++;
else
{
if (prevCharCount > 2) sb.Append(prevCharCount);
else if (prevCharCount == 2) sb.Append(prevChar);
sb.Append(prevChar);
prevChar = c;
prevCharCount = 1;
}
}
if (prevCharCount > 2) sb.Append(prevCharCount);
else if (prevCharCount == 2) sb.Append(prevChar);
sb.Append(prevChar);
return sb.ToString();
}
The method is not too long. But does any one has an idea how to do that in a more concise way using regex? Or LINQ?
How about:
static readonly Regex re = new Regex(@"(\w)(\1){2,}", RegexOptions.Compiled);
static void Main() {
string result = re.Replace("aAAbbbcccc",
match => match.Length.ToString() + match.Value[0]);
}
The regex is a word char, followed by the same (back-ref) at least twice; the lamba takes the length of the match (match.Length
) and appends the first character (match.Value[0]
)
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