正则表达式仅在两个以上的数字时用空格分隔数字

Question

I have a number of string that contain a mix of alphanumeric characters, for example:

10
1234
123-t123b-+1
ff 8765 12

I want to separate the digits by a space, but only if there are three or more digits next to each other. So the above examples would become:

10
1_2_3_4
1_2_3-t1_2_3b-+1
ff 8_7_6_5 12

(added spaces shown with underscored for clarity). Is there a regex that can handle this or do I need to do this programatically?

Answer 1

I think you would need something like this:

var text = "10" + Environment.NewLine + 
           "1234" + Environment.NewLine + 
           "123-t123b-+1" + Environment.NewLine + 
           "ff 8765 12";

var regex = new Regex(@"\d{3,}");
var replacedText = regex.Replace(text, match => string.Join<char>(" ", match.Value));

Answer 2

not sure if C# supports \\G but try this pattern

\B(?=\d{2})|(?<!^)\G(?=\d)

Demo

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here is my second pattern without using \\G

(?<=\d)(?=\d\d)|(?<=\d\d)(?=\d)

Demo
explanation:

(?<=\d)(?=\d\d)     # 0-width after 1 digit and before 2 digits ie 1^234 or 12^34  
|                   # or  
(?<=\d\d)(?=\d)     # 0-width after 2 digits and before 1 digit ie 12^34 or 123^4

Answer 3

i came up with this

match any number followed by two numbers, the second number has to be followed by at least one number and any number digits after that

UPDATE: my pattern can be shortened to: (\\d(?=\\d{2})\\d+)

class Program
{
    static void Main(string[] args)
    {

        string pattern = @"(\d(?=\d{2})\d(?=\d)\d+)";
        string content = "10" + Environment.NewLine +
                         "1234" + Environment.NewLine +
                         "123 - t123b - +1" + Environment.NewLine +
                         "ff 8765 12";

        var reg = new Regex(pattern);
        var replacedText = reg.Replace(content, match => string.Join<char>(" ", match.Value));

        Console.WriteLine(replacedText);

        Console.ReadLine();
    }


}

Answer 4

Using pure regex so far I have been successful in finding position and replacing with a space except when last digit is followed by a whitespace . Here is my solution which is close but up to the mark. If you wish to downvote then do provide some advice in direction of solution.

Regex #1 : (?<=\\d)(?=(\\d)(?=\\d|.))

Explanation : It places the regex pointer by finding a position ( zero width ) preceded by a digit and followed by a digit. Latter digit ( right one ) should be followed by a digit or anything other than whitespaces .

Regex101 Demo#1

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Regex #2 : (?<=\\d)(?=(\\d|\\w)(?=\\d|.))

Explanation : This one has a little variation. It places the regex pointer by finding a position ( zero width ) preceded by a digit and followed by a digit or anything other than whitespaces .

Regex101 Demo #2

Now the only problem left is matching the whitespaces followed by a valid case.