How to delete duplicate values in an array? [duplicate]

Question

Possible Duplicate:
Remove duplicates from array

I have an int array which contains a defined number of elements, all positive. I want to get an array from this one where all the elements appear only once. e.g. If the first array was something like {2000,2011,2011,2012,2009,2009,2000}, I want to get this {2000,2011,2012,2009}. How can I do this? I tried lots of things with for loops but I can't manage to do something good.

Tim Schmelter · Accepted Answer · 2012-05-31 15:50:38Z

8

With LINQ it's easy:

var intArray = new[] { 2000, 2011, 2011, 2012, 2009, 2009, 2000 };
var uniqueArray = intArray.Distinct().ToArray();

http://msdn.microsoft.com/en-us/library/system.linq.enumerable.distinct.aspx

Another way is using Enumerable.GroupBy:

uniqueArray = intArray.GroupBy(i => i).Select(grp => grp.Key).ToArray();

answered May 31, 2012 at 15:50

Tim Schmelter

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Massimiliano Peluso · Accepted Answer · 2012-05-31 16:14:30Z

7

you can do the below

var yourArray = yourArray.Distinct().ToArray();

http://msdn.microsoft.com/en-us/library/system.linq.enumerable.distinct.aspx

edited May 31, 2012 at 16:14

answered May 31, 2012 at 15:49

Massimiliano Peluso

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4 Comments

Wormbo Over a year ago

That will only create an IEnumerable, not an array. To return a new array you need to call ToArray on the result. Something like: yourArray = yourArray.Distinct().ToArray();

Massimiliano Peluso Over a year ago

I have edited my answer even if it was just to give to the OP the right direction to go

Tim S. Over a year ago

Note that the value returned by Distinct is not guaranteed to be ordered. If you want it ordered by the values, use yourArray.Distinct().OrderBy(x=>x).ToArray(). If maintaining the original insertion order is important, (as your example might suggest) you might want to take a slower option like Efthimis's (but I'd recommend List<T> over ArrayList, which is outdated).

Massimiliano Peluso Over a year ago

in this case the order is not important as you can see by looking at the output {2000,2011,2012,2009}

user1263800 · Accepted Answer · 2012-05-31 16:01:54Z

2

Alternative way:

    int[] _array = new int[] {1, 2, 1,2}
    var myArray = new System.Collections.ArrayList();

    foreach(var item in _array){
        if (!myArray.Contains(item))
            myArray.Add(item);
    }

answered May 31, 2012 at 16:01

user1263800

Comments

NominSim · Accepted Answer · 2012-05-31 15:53:04Z

0

In addition to the other answers, you may want to look at a HashSet, especially if you know ahead of time you will have duplicate values.

answered May 31, 2012 at 15:53

NominSim

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