CODEWITHSUNDEEP
c#stringtoken
CBrown77
CBrown77

Reputation: 557

C# More intuitive way to split a string into tokens?

I have a method which takes in a string, which contains various characters, but I'm only concerned about underscores '_' and dollar signs '$'. I want to split up the string into tokens by underscores as each piece b/w the underscores contains important information.

However, if a $ is contained in an area between underscores, then a token should be created from the last occurrence of an underscore to the end (ignoring any underscores in this last section).

Example

input: Hello_To_The$Great_World

expected tokens: Hello, To, The$Great_World

Question

I have a solution below, but I'm wondering is there a cleaner/more intuitive way of doing this than what I have below?

var aTokens = new List<string>();
var aPos = 0;
for (var aNum = 0; aNum < item.Length; aNum++)
{
    if (aNum == item.Length - 1)
    {
        aTokens.Add(item.Substring(aPos, item.Length - aPos));
        break;
    }               
    if (item[aNum] == '$')
    {
        aTokens.Add(item.Substring(aPos, item.Length - aPos));
        break;
    }
    if (item[aNum] == '_')
    {
    aTokens.Add(item.Substring(aPos, aNum - aPos));
    aPos = aNum + 1;
    }
}

Upvotes: 1

Views: 1839

Answers (3)

Dave C
Dave C

Reputation: 231

Here's my version (loops are so last year...)

const char dollar = '$';
const char underscore = '_';

var item = "Hello_To_The$Great_World";
var aTokens = new List<string>();

int dollarIndex = item.IndexOf(dollar);
if (dollarIndex >= 0)
{
    int lastUnderscoreIndex = item.LastIndexOf(underscore, dollarIndex);
    if (lastUnderscoreIndex >= 0)
    {
        aTokens.AddRange(item.Substring(0, lastUnderscoreIndex).Split(underscore));
        aTokens.Add(item.Substring(lastUnderscoreIndex + 1));
    }
    else
    {
        aTokens.Add(item);
    }
}
else
{
    aTokens.AddRange(item.Split(underscore));
}

Edit:

I should have added, cleaner/more intuitive is very subjective, as you have found out by the variety of answers provided. From a maintainability point of view, it's much more important that the method you write to do the parsing is unit tested!

It's also an interesting exercise to test the performance of the various methods posted here - it quickly becomes apparent that your original version is much faster than using regular expressions! (Although in a real life situation, it's probably quite unlikely that the performance of this method will make any difference to your application!)

Upvotes: 1

Ulugbek Umirov
Ulugbek Umirov

Reputation: 12797

You can split string by _ not having $ before them.

For that you can use the following regex:

(?<!\$.*)_

Sample code:

string input = "Hello_To_The$Great_World";
string[] output = Regex.Split(input, @"(?<!\$.*)_");

You also can do the task without regex and without loops, but with the help of 2 splits:

string input = "Hello_To_The$Great_World";
string[] temp = input.Split(new[] { '$' }, 2);
string[] output = temp[0].Split('_');
if (temp.Length > 1)
    output[output.Length - 1] = output[output.Length - 1] + "$" + temp[1];

Upvotes: 3

myermian
myermian

Reputation: 32505

This method is not efficient or clean, but it gives you a general idea of how to do this:

  1. Split your string into tokens
  2. Find the index of the first string to contain $
  3. Return a new array with the first n tokens and the final token is the remaining strings concatenated.

It's probably more useful to take advantage of IEnumerable or do things over a for loop instead of all this Array.Copy stuff... but you get the gist of it.

private string[] SomeMethod(string arg)
{
    var strings = arg.Split(new[] { '_' });

    var indexedValue = strings.Select((v, i) => new { Value = v, Index = i }).FirstOrDefault(x => x.Value.Contains("$"));

    if (indexedValue != null)
    {
        var count = indexedValue.Index + 1;

        string[] final = new string[count];
        Array.Copy(strings, 0, final, 0, indexedValue.Index);
        final[indexedValue.Index] = String.Join("_", strings, indexedValue.Index, strings.Length - indexedValue.Index);
        return final;
    }

    return strings;
}

Upvotes: 1

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