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, Jan 18 '16 at 17:01
[Many](https://www.google.ch/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=c%23+string+split+keep+delimiter) 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; }` ? — , Jan 18 '16 at 17:01

score 2 · Accepted Answer · edited Jan 18 '16 at 17:38

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 '16 at 17:38

Frank Bryce

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answered Jan 18 '16 at 17:10

TVOHM

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Thank you, I think this is going to be the best I can do without a .Net library call that does it for me. – Frank Bryce Jan 18 '16 at 17:13

Camilo Terevinto · Answer 2 · 2016-01-18T17:12:48.927

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 '16 at 17:12

answered Jan 18 '16 at 17:04

Camilo Terevinto

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What happens if `inStr` has the delimiter at the end? – Frank Bryce Jan 18 '16 at 17:05
@JohnCarpenter RemoveEmptyEntries will remove the delimiter at the end because it will be an empty string – Camilo Terevinto Jan 18 '16 at 17:06
Which is not what I want. I'll update my question to be more clear. – Frank Bryce Jan 18 '16 at 17:07
@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.. – MethodMan Jan 18 '16 at 17:09
@JohnCarpenter see my edit, something like that is what I could understand. – Camilo Terevinto Jan 18 '16 at 17:13

score 0 · Answer 3 · answered Nov 23 '18 at 15:15

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);
        }
    }

Split string and keeping the delimiter without Regex C#

3 Answers3