Remove item from a simple array one time

Question

How to remove item from a simple array once? For example, a char array contains these letters:

a,b,d,a

I would like to remove the letter "a" one time, then the result would be:

a,b,d

Do you want distinct values or you just want to remove a single character once, e.g. if you have `a,b,b,d,a` and you want to remove `a` then would it be `a,b,b,d` — user2711965, Oct 03 '13 at 15:33
Yes, if I have a,b,b,d,a and I want to remove "a" then would it be a,b,b,d — user2843341, Oct 03 '13 at 15:34
What about `a,a,b,b,d,a` should it be `a,a,b,b` ? do you want to remove from the end ? — user2711965, Oct 03 '13 at 15:35
If you have a,b,b,d,a how doe you specify you want the second a removed, not the first a? Do you already know the index of the item you want removed? — hatchet - done with SOverflow, Oct 03 '13 at 15:36
possible duplicate of [Remove element of a regular array](http://stackoverflow.com/questions/457453/remove-element-of-a-regular-array) — huMpty duMpty, Oct 03 '13 at 15:39
My guess is your teacher is setting you up to appreciate more advanced data structures. — rheitzman, Oct 03 '13 at 15:43

score 2 · Answer 1 · answered Oct 03 '13 at 15:38

Removing an item from an array is not really possible. The size of an array is immutable once allocated. There is no way to remove an element per say. You can overwrite / clear an element but the size of the array won't change.

If you want to actually remove an element and change the size of the collection then you should use List<char> instead of char[]. Then you can use the RemoveAt API

List<char> list = ...;
list.RemoveAt(3);

Reed Copsey · Accepted Answer · 2013-10-03T15:41:39.540

0

If your goal is to just skip the first 'a', then remove the second, you could use something like:

int first = Array.IndexOf(theArray, 'a');
if (first != -1)
{
    int second = Array.IndexOf(theArray, 'a', first+1);
    if (second != -1)
    {
    theArray = theArray.Take(second - 1).Concat(theArray.Skip(second+1)).ToArray();
    }
}

If you just need to remove any of the 'a' characters (since you specified that the order is not relevant), you could use:

int index = Array.IndexOf(theArray, 'a');
if (index != -1)
{
    theArray = theArray.Take(index - 1).Concat(theArray.Skip(index+1)).ToArray();
}

Note that these don't actually remove the item from the array - they create a new array with that element missing from the newly created array. Since arrays are not designed to change in total length once created, this is typically the best alternative.

If you will be doing this frequently, you may want to use a collection type that does allow simple removal of elements. Switching from an array to a List<char>, for example, makes removal far simpler, as List<T> supports simple APIs such as use List<T>.Remove directly.

edited Oct 03 '13 at 15:41

answered Oct 03 '13 at 15:36

Reed Copsey

554,122
78
1,158
1,373

1

Note that this is not removing an item from the array. The array is unchanged. This is creating a new array that has all of the values of the previous array, except for one. It's an important distinction. – Servy Oct 03 '13 at 15:37
But if "a" is not in the first position, but b,a,d,a? – user2843341 Oct 03 '13 at 15:39
@user2843341 Both of these options will handle that without issue. – Reed Copsey Oct 03 '13 at 15:40
1

@user2843341: that why its using `indexof` – huMpty duMpty Oct 03 '13 at 15:40

score 0 · Answer 3 · answered Oct 03 '13 at 15:45

0

You can use linq by trying the following

var someArray= new string[3];
someArray[0] = "a";
someArray[1] = "b";
someArray[2] = "c";

someArray= someArray.Where(sa => !sa.Equals("a")).ToArray();

Please note: This method is not removing the element from the array but that it is creating a new array that is excluding the element. This may have an effect on performance.

You might consider using a list or collection.

answered Oct 03 '13 at 15:45

Andre Lombaard

6,985
13
55
96

this would remove all the 'a' characters not just one of them – Weyland Yutani Oct 03 '13 at 15:49

score 0 · Answer 4 · answered Oct 03 '13 at 15:57

static void Main(string[] args)
{
    char[] arr = "aababde".ToArray();
    arr = RemoveCharacter(arr, 'a');
    arr = RemoveCharacter(arr, 'b');
    arr = RemoveCharacter(arr, 'd');
    arr = RemoveCharacter(arr, 'z');
    arr = RemoveCharacter(arr, 'a');
    //result is 'a' 'b' 'e'
}

static char[] RemoveCharacter(char[] array, char c)
{
    List<char> list = array.ToList();
    list.Remove(c);
    return list.ToArray();
}

Remove item from a simple array one time

4 Answers4