Replacing multiple consecutive spaces by a single space in a string

Question

I currently have this class to replace consecutive spaces by one:

public static string RemoveSpacesLoop(string value)
{
   if(value.Contains("  "))
   {
       return RemoveSpacesLoop(value.Replace("  ", " "));
   }
   else
   {
       return value;
   }
}

It works, but in the long run it may cause performance issues. is there a way to simplify this ?

What's the point for the recursive call? According to docs, Replace returns "A string that is equivalent to the current string except that all instances of oldValue are replaced with newValue." — Andrei, Jan 28 '15 at 13:05
Have you compared the performance to doing it as a `while` loop? — Rowland Shaw, Jan 28 '15 at 13:05
I suppose you want to collapse multiple spaces into one, not generally "remove spaces"?? — Peter - Reinstate Monica, Jan 28 '15 at 13:06
@tom He wants to replace multiple spaces with a single space, not remove them entirely. — DGibbs, Jan 28 '15 at 13:07
A good specification is the first step towards a good program. — Peter - Reinstate Monica, Jan 28 '15 at 13:08
It can be done with a single pass copying array of characters. Copy by character, remember when space was copied to skip copying further consecutive spaces. Make 2 passes to know destination array size or use list. — Sinatr, Jan 28 '15 at 13:13

Andrey Korneyev · Answer 1 · 2015-01-28T13:26:04.903

7

You can use Regex. For example:

var x = "123  456 789    999   0";
var y = Regex.Replace(x, @"\s{2,}", " ");

It will replace all multiple spaces with single one.

You can also iterate over characters in string and produce new string comparing that characters with spaces something like this:

StringBuilder sb = new StringBuilder();
bool isSpaceFound = false;

foreach (char c in x)
{
    if (c == ' ')
    {
        if (!isSpaceFound)
            sb.Append(c);

        isSpaceFound = true;
    }
    else
    {
        isSpaceFound = false;
        sb.Append(c);
    }
}

var y = sb.ToString();

edited Jan 28 '15 at 13:26

answered Jan 28 '15 at 13:05

Andrey Korneyev

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Explanation: \s is regex syntax for space {2,} means 2 consecutive or more. So this regular expression looks for 2 or more consecutive spaces and replaces them with a single space. – hollystyles Jan 28 '15 at 13:08
problem with this is that it is slow @andykomeyev – user3702989 Jan 28 '15 at 13:09
@user3702989 how long are strings you are working with? For Regex to be slow it should be very long strings - probably megabytes of length. – Andrey Korneyev Jan 28 '15 at 13:11
@user3702989 You can't just say "...it is slow" without any qualification. Compared to snails it is lightening quick. Define slow. – hollystyles Jan 28 '15 at 13:13
@AndyKorneyev they can be anything from 25 to 1 – user3702989 Jan 28 '15 at 13:13
@user3702989 "*from 25 to 1*"? What does it means? What is your measurement units? Is it string length or spaces count? – Andrey Korneyev Jan 28 '15 at 13:14
@AndyKorneyev that is string length – user3702989 Jan 28 '15 at 13:16
@user3702989 and what is measurement units of that "25"? bytes, kilobytes, megabytes? – Andrey Korneyev Jan 28 '15 at 13:17
@user3702989 Anyway, if you don't want to use regexes - you can iterate characters from string one-by-one and do some simple comparison. I've updated the answer with the sample. And yes, I really doubt that method to join multiple spaces faster than this exists . ;) – Andrey Korneyev Jan 28 '15 at 13:30
@AndyKorneyev its a string of 25 characters – user3702989 Jan 28 '15 at 13:31
@user3702989 Oh, trust me - regex can't be really slow on a string of 25 characters. It can be slightly slower than iterating character one-by-one, but difference is insignificant – Andrey Korneyev Jan 28 '15 at 13:35

Replacing multiple consecutive spaces by a single space in a string

1 Answers1