List of String in c#

Question

1.00/5 (2 votes)

See more:

Hi,
i have list of string filling like this

station1|debit
station1|volume
station2|pluit
station2|debit
station3|debit
station4|debit

and i want know count of station like

station1 ==>2 
station3 ==>1

Posted 14-Apr-15 0:26am

Member 11573837

Updated 14-Apr-15 0:50am

Maciej Los

v3

Add a Solution

Comments

Maciej Los 14-Apr-15 6:56am

How exactly your list look like?

3 solutions

Solution 1

If i understand you correctly...

C#

List<string[]> sta = new List<string[]>(){
  new string[]{"station1", "debit"},
  new string[]{"station1", "volume"},
  new string[]{"station2", "pluit"},
  new string[]{"station2", "debit"},
  new string[]{"station3", "debit"},
  new string[]{"station4", "debit"}};

  var qry = sta.GroupBy(a=>a[0]).Select(grp=>new{station = grp.Key, count= grp.Count()});

  foreach(var r in qry)
  {
      Console.WriteLine("{0} - {1}", r.station, r.count);
  }

[EDIT]
In case of pipe "|" delimiter:

C#

List<string> sta = new List<string>(){"station1|debit",
"station1|volume",
"station2|pluit",
"station2|debit",
"station3|debit",
"station4|debit"};

var qry = sta.Select(a=>Tuple.Create(a.Split('|')[0], a.Split('|')[1]))
            .GroupBy(b=>b.Item1).Select(grp=>new{station=grp.Key, count = grp.Count()});

Posted 14-Apr-15 0:59am

Maciej Los

Updated 14-Apr-15 1:19am

v2

Comments

Florian Braun 14-Apr-15 7:04am

I like your solution

Maciej Los 14-Apr-15 7:13am

Thank you ;)

Florian Braun 14-Apr-15 7:19am

I changed your solution a little bit :)

Member 11573837 14-Apr-15 7:09am

hi,
i don't have liste declared like this
List<string[]> sta = new List<string[]>();

i have
List<string> lst_Station = new List<string>();
and (station1|debit) it one string the pipe is juste deminateur

Florian Braun 14-Apr-15 7:21am

arrg.. yours is obviously a lot more compact. i so need to learn linq

Maciej Los 14-Apr-15 7:24am

Thank you, Florian ;)

Sergey Alexandrovich Kryukov 14-Apr-15 11:14am

That will work, but is not the best approach. This is not just array of strings, this is a key-value pair probably with fixed semantics. The problem of second approach is splitting strings (or doing anything else) again and again. At the same time, it's apparent that presenting data in this way is ugly; the data hardly should be key in this form (if even created in this form).

Please see my answer (Solution 3).

—SA

Solution 3

You just need different data structure designed for fast search. For example, it could be

C#

class Station {
   internal uint Count { get; set; }
   internal string Name { get; set; } // "volume", etc
}
// then you could use 
var dictionary = new System.Collections.Generic.Dictionary<string, Station>;

Or you could use the structure encapsulating two dictionaries, one for finding "volume" and number by "station1", and another for funding "station1" by "volume" (I don't know what they mean, so I'm explaining it by example).

Dictionaries give you time complexity of O(1), that's why. So, it can be very beneficial for any considerable number of items. The use of reference types for all elements makes redundancy pretty low.

You can parse all your strings with '|' using string.Split just once, and then quickly work with your structures.

[EDIT]

You can add split string line by line and check is the key already exists. Use Dictionary.TryGetValue, because you also need to get the value of the key already exists. If it exist, just increment Count.

Dictionary.TryGetValue lookup will give you O(1) complexity.

[END EDIT]

Please see:
http://en.wikipedia.org/wiki/Hash_table,
http://en.wikipedia.org/wiki/Associative_array (this is how dictionaries work),
http://en.wikipedia.org/wiki/Time_complexity,
http://en.wikipedia.org/wiki/Big_O_notation.

—SA

Posted 14-Apr-15 5:04am

Sergey Alexandrovich Kryukov

Updated 14-Apr-15 7:20am

v4

Comments

Maciej Los 14-Apr-15 12:35pm

Sorry, Sergey, but i have one question: am i blind or you took a shortcut too much? I'm not sure how to use dictionary in this context.

Sergey Alexandrovich Kryukov 14-Apr-15 12:48pm

Sorry, it looks like I misformatted the code, so I fixed it now.
Are you saying that something is not clear, need more explanation?
Well, in this sample, the key is a string like "station1", and the value is the structure. And the search is done by "station1", using Dictionary.TryGetValue.

More generally: I repeated many times, it's one of the worst present-day fallacies, to work with strings representing data, instead of data itself. This example shows that even string data should not be represented using just the class System.String.

—SA

Maciej Los 14-Apr-15 12:59pm

The last statement is completely clear, but i think you need to explain it bit more. BTW: what data type is uing?

Sergey Alexandrovich Kryukov 14-Apr-15 13:09pm

Typo. Thank you, I'll fix it and add more explanation.
—SA

Maciej Los 14-Apr-15 13:27pm

I think you missed another one thing. Count couldn't be a Station class property/field. It always should be one, because each station have to be unique. Another class (which inherits from ICollectionBase - for example) should be a container for Station and Something what describes "debit", "pluit", "volume". This is how the skeleton have to look like ;)

Sergey Alexandrovich Kryukov 14-Apr-15 15:10pm

It's just the matter of naming. I don't really know what is the station. The semantic we know so far apparently deals with object described it as this class. Call it "DescriptorOfTheSetOfObjectsWithIdenticalName" or "NameWithCardinality". This is all what's required to answer the inquirer's question.

The thing is: from this answer, I have no idea what "station1" represent, is it really a station of not; and I have no idea what object is represented by "volume" or "debit". I call the property "Name", but I have no idea if the role of it is name or not. It's also possible that correct data structure would be enum RoleOrSomething { volume, debit, ... }. By the way, this lack of understanding is just one more consequence of the attempt to use string representing data instead of real structured data. Metadata conducted by .NET (or other system's) type definition is completely lost.

Bad idea in first place. What I suggest is to fix it, and what I suggest should be considered as a rough idea.

—SA

Sergey Alexandrovich Kryukov 14-Apr-15 13:21pm

Done. Thank you.
—SA

Maciej Los 14-Apr-15 13:28pm

You've been faster then me. Please, see my previous comment.

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Florian Braun · Accepted Answer · 2015-04-14T01:17:00

Solution 2

C#

public static void Main(string[] args)
        {
            List<string> sta1 = new List<string>();
            sta1.Add("station1|debit");
            sta1.Add("station1|volume");
            sta1.Add("station2|pluit");
            sta1.Add("station2|debit");
            sta1.Add("station3|debit");
            sta1.Add("station4|debit");

            List<string[]> sta = new List<string[]>();
            foreach (string s in sta1)
                sta.Add(s.Split('|'));


  var qry = sta.GroupBy(a=>a[0]).Select(grp=>new{station = grp.Key, count= grp.Count()});

  foreach(var r in qry)
  {
      Console.WriteLine("{0} - {1}", r.station, r.count);
  }

Posted 14-Apr-15 1:17am

Florian Braun

Comments

Maciej Los 14-Apr-15 7:21am

5ed!
See updated answer (after EDIT). I use Tuple, so... there's no need to create another List<arrayofstring> ;)

Tomas Takac 14-Apr-15 7:21am

+5, although it could be written as a one-liner ;-)
var output = input.Select(x => x.Split('|')).GroupBy(x => x[0]).Select(x => new { Name = x.Key, Count = x.Count()});

Maciej Los 14-Apr-15 7:22am

Good catch, Tomas ;)

Florian Braun 14-Apr-15 7:23am

thats a realy good one

Member 11573837 14-Apr-15 7:31am

Big Thanks

Sergey Alexandrovich Kryukov 14-Apr-15 11:14am

That will work, but is not the best approach. This is not just array of strings, this is a key-value pair probably with fixed semantics. The problem of second approach is splitting strings (or doing anything else) again and again. At the same time, it's apparent that presenting data in this way is ugly; the data hardly should be key in this form (if even created in this form).

Please see my answer (Solution 3).

—SA