Find unique strings for a string array
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Hello everyone, I have a string array, but may have duplicate strings. Any built-in or smart way to remove the duplicate ones and generate a string array contains only unique ones? For example, the input array is {"abc", "bcd", "abc"}, the unique output array is {"abc", "bcd"}. thanks in advance, George
Not sure why people are saying there isn't a built in set class. Use Hashset< string>. Insertion and checking for existing values is roughly O(n). Has extension methods on it for doing linqy kind of things. Also noticed a lot of people said "use linq!". Linq does not make things run faster - it's not a magic replacement for Array.Find. It just makes your code look pretty, thats all :D
Mark Churchill Director, Dunn & Churchill Pty Ltd Free Download: Diamond Binding: The simple, powerful, reliable, and effective data layer toolkit for Visual Studio.
Alpha release: Entanglar: Transparant multiplayer framework for .Net games. -
You can use the Distinct method(an Extention Method) if you are using C#3.0 and the implementation code is quit simple, such as: string[] strs = new string[] { "abc", "bcd", "abc" }; IEnumerable newStrs = strs.Distinct(); Hope this will help. LuckyBoy
LuckyBoy, Distinct belongs to .Net 3.5, and I have to use .Net 3.0. :-) Any ideas for .Net 3.0? regards, George
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LuckyBoy, Distinct belongs to .Net 3.5, and I have to use .Net 3.0. :-) Any ideas for .Net 3.0? regards, George
George_George wrote:
I have to use .Net 3.0
Then I can't suggest HashSet. :( But I can suggest my Set class. :-D
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Make a custom function,In which create an a generic as taken below a list. List<string> UnqueList=new List<string>(); for (int i = 0; i < strarr.Length; i++) { if(!UnqueList.Exists(strarr[0])) { UnqueList.Add(strarr[0]); } } Now you'll the list conatining unique elements.You can conert it to array too as UnqueList.ToArray();
Cheers!! Brij
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Not sure why people are saying there isn't a built in set class. Use Hashset< string>. Insertion and checking for existing values is roughly O(n). Has extension methods on it for doing linqy kind of things. Also noticed a lot of people said "use linq!". Linq does not make things run faster - it's not a magic replacement for Array.Find. It just makes your code look pretty, thats all :D
Mark Churchill Director, Dunn & Churchill Pty Ltd Free Download: Diamond Binding: The simple, powerful, reliable, and effective data layer toolkit for Visual Studio.
Alpha release: Entanglar: Transparant multiplayer framework for .Net games.Thanks Mark, I think people means no built-in single call for find the uniqueness for string. BTW: if LINQ is slow, why people will use LINQ? regards, George
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George_George wrote:
I have to use .Net 3.0
Then I can't suggest HashSet. :( But I can suggest my Set class. :-D
What are the advantages of your Set class over .Net Set class? regards, George
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List<string> newArray = new List<string>();
foreach (string token in yourArray)
{
if (!newArray.Contains(token))
{
newArray.Add(token);
}
}Thanks Igor, I like your solution! :-) regards, George
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Thanks Mark, I think people means no built-in single call for find the uniqueness for string. BTW: if LINQ is slow, why people will use LINQ? regards, George
*shrug* I think Hashset< T>.Add(T item) returning bool if it was unique is close enough. People use LINQ because it makes the code more readable. Generally CPU is cheap and good programmers aren't. Its ok to have a 10% overhead if your code is more reliable and easier to maintain as a result.
Mark Churchill Director, Dunn & Churchill Pty Ltd Free Download: Diamond Binding: The simple, powerful, reliable, and effective data layer toolkit for Visual Studio.
Alpha release: Entanglar: Transparant multiplayer framework for .Net games. -
Make a custom function,In which create an a generic as taken below a list. List<string> UnqueList=new List<string>(); for (int i = 0; i < strarr.Length; i++) { if(!UnqueList.Exists(strarr[0])) { UnqueList.Add(strarr[0]); } } Now you'll the list conatining unique elements.You can conert it to array too as UnqueList.ToArray();
Cheers!! Brij
Thanks Brij! The "generic" you mean List? regards, George
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Thanks Igor, I like your solution! :-) regards, George
no worries ;)
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*shrug* I think Hashset< T>.Add(T item) returning bool if it was unique is close enough. People use LINQ because it makes the code more readable. Generally CPU is cheap and good programmers aren't. Its ok to have a 10% overhead if your code is more reliable and easier to maintain as a result.
Mark Churchill Director, Dunn & Churchill Pty Ltd Free Download: Diamond Binding: The simple, powerful, reliable, and effective data layer toolkit for Visual Studio.
Alpha release: Entanglar: Transparant multiplayer framework for .Net games.Mark Churchill wrote:
Generally CPU is cheap and good programmers aren't
That's a good one :)
Navaneeth How to use google | Ask smart questions
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Thanks Christian, What do you mean "have a list inside"? I am talking about string array, I am not sure where is the list you are talking about. Show some pseudo code? regards, George
public class set { private List theList; public bool Add(T item) { if (theList.Contains(item)) return false; theList.Add(item); return true; } } This is the start of a set class, a container that only contains one of any object.
Christian Graus Driven to the arms of OSX by Vista.
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Thanks Brij! The "generic" you mean List? regards, George
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Thanks Mark, I think people means no built-in single call for find the uniqueness for string. BTW: if LINQ is slow, why people will use LINQ? regards, George
George_George wrote:
BTW: if LINQ is slow, why people will use LINQ?
I think Mark is right. We can get the benefits from LINQ for integrating the data and object. But I am not sure about the performance of LINQ. Though I do believe Mircosoft would make greate efforts to improve it.
LuckyBoy
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Hello everyone, I have a string array, but may have duplicate strings. Any built-in or smart way to remove the duplicate ones and generate a string array contains only unique ones? For example, the input array is {"abc", "bcd", "abc"}, the unique output array is {"abc", "bcd"}. thanks in advance, George
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*shrug* I think Hashset< T>.Add(T item) returning bool if it was unique is close enough. People use LINQ because it makes the code more readable. Generally CPU is cheap and good programmers aren't. Its ok to have a 10% overhead if your code is more reliable and easier to maintain as a result.
Mark Churchill Director, Dunn & Churchill Pty Ltd Free Download: Diamond Binding: The simple, powerful, reliable, and effective data layer toolkit for Visual Studio.
Alpha release: Entanglar: Transparant multiplayer framework for .Net games.Thanks Mark, 1. "*shrug* I think Hashset< T>.Add(T item) returning bool if it was unique is close enough." -- I am still confused why do you think .Net built-in Hashset is good enough. Any comments? 2. I know about LINQ but not very experienced. My concern about LINQ is, I do not think it is more readable, why do you think it is more readable? 3. LINQ is only 10% slower? I think it is much slower in my experience. Do you have any performance benchmarking data? regards, George
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What are the advantages of your Set class over .Net Set class? regards, George
Operators.
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George_George wrote:
BTW: if LINQ is slow, why people will use LINQ?
I think Mark is right. We can get the benefits from LINQ for integrating the data and object. But I am not sure about the performance of LINQ. Though I do believe Mircosoft would make greate efforts to improve it.
LuckyBoy
In my experience and other guys besides me, the performnace feedback of LINQ is bad. :-) What about yours? regards, George
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Sounds to me like you should be using a set data structure, if you never need the duplicate strings.
At university studying Software Engineering - if i say this line to girls i find they won't talk to me Dan
Thanks Dan! But there is no such data structure in .Net, correct? regards, George
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public class set { private List theList; public bool Add(T item) { if (theList.Contains(item)) return false; theList.Add(item); return true; } } This is the start of a set class, a container that only contains one of any object.
Christian Graus Driven to the arms of OSX by Vista.
Thanks Christian, I like your idea. I am surprised why there is no built-in Set class in .Net. :-) regards, George