Removing similar characters in a string

Question

Is there any built-in method to remove similar characters in a string?
Examples:

aaaabbbccc ->  abc
aabbccaa -> abc

Thanks

Answer 1

I would have thought you want to look at using Regular Expressions. For C# .NET this is a useful site...

http://www.regular-expressions.info/dotnet.html

Answer 2

no.

But can easly be made in a loop, remember you need to build a new string you cannot edit a char in a existing string ( you can do string.remove , but very likely gonna be slow and mess up your loop ).

basicly:

for(int i=0;i<MyText.Length;i++)
{
   if(i == 0)
     contiune;

   if(Text[i] == Text[i - 1])
       // Do something, both chars are the same
}

Answer 3

Use the Regex class:

Regex.Replace( "aaabbcc", @"(\w)\1+", "$1" )

will result in

abc

For more infos look here.

EDIT:
Since you I edited your question:

Regex.Replace( "acaabbccbaa", @"(\w)(?<=\1.+)", "" )

will result in

acb

This pattern uses a negative lookbehind to identify doubled chars and replaces them by ""

Answer 4

You could use a HashSet and build an extension method for this:

    static string RemoveDuplicateChars(this string s)
    {
        HashSet<char> set = new HashSet<char>();
        StringBuilder sb = new StringBuilder(s.Length);

        foreach (var c in s)
        {
            if (set.Add(c))
            {
                sb.Append(c);
            }
        }

        return sb.ToString();
    }

or using Enumerable.Distinct, simply:

Console.WriteLine(new string("aaabbbccaddcacc".Distinct().ToArray()));

Answer 5

Does something like this solve your problem?

string distinct = new string("aaaabbbccc".Distinct().ToArray());

It's a little ugly, but you could wrap it into an extension method:

public static string UniqueChars(this string original)
{
    return new string(original.Distinct().ToArray());
}

Hope this helps.

Answer 6

Since you specifically asked about removing "similar" characters, you may want to try something like this:

using System.Globalization;
....
        private string RemoveDuplicates(string text)
        {
            StringBuilder result = new StringBuilder();
            string previousTextElement = string.Empty;
            TextElementEnumerator textElementEnumerator = StringInfo.GetTextElementEnumerator(text);
            textElementEnumerator.Reset();
            while (textElementEnumerator.MoveNext())
            {
                string textElement = (string)textElementEnumerator.Current;
                if (string.Compare(previousTextElement, textElement, CultureInfo.InvariantCulture,
                    CompareOptions.IgnoreCase | CompareOptions.IgnoreNonSpace |
                    CompareOptions.IgnoreWidth) != 0)
                {
                    result.Append(textElement);
                    previousTextElement = textElement;
                }
            }
            return result.ToString();
        }