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
May be
Array.FindAllcan help you. Check out MSDN for it. Another way could be: 1. Create a list/hashtable. Then loop through the array. 2. Check if the element exists in the list/hashtable. 3. If it does its a duplicate value. Remove it from array. 4. If it doesnt add it to the list/hashtable.C isn't that hard: void (*(*f[])())() defines f as an array of unspecified size, of pointers to functions that return pointers to functions that return void "Always program as if the person who will be maintaining your program is a violent psychopath that knows where you live." - Martin Golding
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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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Hi Brij, "some generic for that" -- do you have some more words on this? Or some pseudo code? regards, George
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from what I know there's no such thing and you'd have to iterate thru and pick the unique ones manually. it's not that difficult you know ;)
Thanks Igor, Good to know .Net does not provide such a class. :-) regards, George
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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
If I'm not mistaken you can use LINQ to select unique values.
Giorgi Dalakishvili #region signature My Articles Asynchronous Registry Notification Using Strongly-typed WMI Classes in .NET [^] My blog #endregion
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Hi Brij, "some generic for that" -- do you have some more words on this? Or some pseudo code? regards, George
List<string> newArray = new List<string>();
foreach (string token in yourArray)
{
if (!newArray.Contains(token))
{
newArray.Add(token);
}
} -
If I'm not mistaken you can use LINQ to select unique values.
Giorgi Dalakishvili #region signature My Articles Asynchronous Registry Notification Using Strongly-typed WMI Classes in .NET [^] My blog #endregion
...yes, assuming he's using .net 3+
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I dunno why a set class is not included, but it's easy to write one. Just have a list inside, and check if an entry exists before adding it.
Christian Graus Driven to the arms of OSX by Vista.
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
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If I'm not mistaken you can use LINQ to select unique values.
Giorgi Dalakishvili #region signature My Articles Asynchronous Registry Notification Using Strongly-typed WMI Classes in .NET [^] My blog #endregion
LINQ is good, but I have to use .Net 3.0, not .Net 3.5. Any ideas for .Net 3.0 based solution? :-) regards, George
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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
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
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...yes, assuming he's using .net 3+
Yes, I have to use .Net 3.0, not .Net 3.5. Any ideas for .Net 3.0 based solution? I think LINQ belongs to .Net 3.5, not .Net 3.0? regards, George
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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