Split string and keeping the delimiter without Regex C#

Question

Problem: spending too much time solving simple problems. Oh, here's the simple problem.

Input: string inStr, char delimiter
Output: string[] outStrs where string.Join("", outStrs) == inStr and each item in outStrs before the last item must end with the delimiter. If inStr ends with the delimiter, then the last item in outStrs ends with the delimiter as well.

Example 1:

Input: "my,string,separated,by,commas", ','
Output: ["my,", "string,", "separated,", "by,", "commas"]

Example 2:

Input: "my,string,separated,by,commas,", ','
Output: ["my,", "string,", "separated,", "by,", "commas,"] (notice trailing comma)

Solution with Regex: here

I want to avoid using Regex, simply because this requires only character comparison. It's algorithmically just as complex to do as what string.Split() does. It bothers me that I cannot find a more succinct way to do what I want.

My bad solution, which doesn't work for me... it should be faster and more succinct.

var outStr = inStr.Split(new[]{delimiter}, 
                         StringSplitOptions.RemoveEmptyEntries)
                  .Select(x => x + delimiter).ToArray();
if (inStr.Last() != delimiter) {
    var lastOutStr = outStr.Last();
    outStr[outStr.Length-1] = lastOutStr.Substring(0, lastOutStr.Length-1);
}

@James I don't need to use the power of regular expressions. It's a simple character comparison. It feels like too big of a tool. This problem isn't any harder than the string.Split() method, the functionality just needs to be slightly different. — Frank Bryce
– Frank Bryce, Commented Jan 18, 2016 at 17:01
Many solved that with Regex. Is there any chance in appending the delimiter when you are using the values? something like: foreach(string token in outStrs) { string value = token + delimiter; } ? — user2894316
– user2894316, Commented Jan 18, 2016 at 17:01

Frank Bryce · Accepted Answer · 2016-01-18 17:38:39Z

2

Using LINQ:

string input = "my,string,separated,by,commas";
string[] groups = input.Split(',');
string[] output = groups
    .Select((x, idx) => x + (idx < groups.Length - 1 ? "," : string.Empty))
    .Where(x => x != "")
    .ToArray();

Split the string into groups, then transform every group that is not the last element by appending a comma to it.

Just thought of another way you could do it, but I don't think this method is as clear:

string[] output = (input + ',').Split( new[] { "," }, StringSplitOptions.RemoveEmptyEntries)
    .Select(x => x + ',').ToArray();

edited Jan 18, 2016 at 17:38

Frank Bryce

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answered Jan 18, 2016 at 17:10

TVOHM

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1 Comment

Frank Bryce Over a year ago

Thank you, I think this is going to be the best I can do without a .Net library call that does it for me.

Camilo Terevinto · Accepted Answer · 2016-01-18 17:12:48Z

0

Seems pretty simple to me without using Regex:

string inStr = "dasdasdas";
char delimiter = 'A';
string[] result = inStr.Split(new string[] { inStr }, System.StringSplitOptions.RemoveEmptyEntries);
string lastItem = result[result.Length - 1];
int amountOfLoops = lastItem[lastItem.Length - 1] == delimiter ? result.Length - 1 : result.Length - 2;
for (int i = 0; i < amountOfLoops; i++)
{
    result[i] += delimiter;
}

edited Jan 18, 2016 at 17:12

answered Jan 18, 2016 at 17:04

Camilo Terevinto

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5 Comments

Frank Bryce Over a year ago

What happens if inStr has the delimiter at the end?

Camilo Terevinto Over a year ago

@JohnCarpenter RemoveEmptyEntries will remove the delimiter at the end because it will be an empty string

Frank Bryce Over a year ago

Which is not what I want. I'll update my question to be more clear.

MethodMan Over a year ago

@JohnCarpenter can you post an exact example of the string input that you are using.. does it really include double quotes as well as single quotes..

Camilo Terevinto Over a year ago

@JohnCarpenter see my edit, something like that is what I could understand.

Vahid Borandeh · Accepted Answer · 2018-11-23 15:15:48Z

0

public static IEnumerable<string> SplitAndKeep(this string s, string[] delims)
    {
        int start = 0, index;
        string selectedSeperator = null;
        while ((index = s.IndexOfAny(delims, start, out selectedSeperator)) != -1)
        {
            if (selectedSeperator == null)
                continue;
            if (index - start > 0)
                yield return s.Substring(start, index - start);
            yield return s.Substring(index, selectedSeperator.Length);
            start = index + selectedSeperator.Length;
        }

        if (start < s.Length)
        {
            yield return s.Substring(start);
        }
    }

answered Nov 23, 2018 at 15:15

Vahid Borandeh

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