Deleting Last Item from Array of String

Question

I'm working on a simple blackjack game project. Firstly I create the array of cards:

string[] deck = { "2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K", "A", };

than I multiply it 4 and given deckNumber:

newDeck = Enumerable.Repeat(deck, deckNumber*4).SelectMany(x => x).ToArray();

when I want to delete last card from array I apply this:

newDeck = newDeck.Where(w => w != newDeck.Last()).ToArray();

so the problem is that code doesn't removes last item from array, acts like there are multiple arrays and removes all last elements from them. For example with one deck:

cards: 2 3 4 5 6 7 8 9 10 J Q K A 2 3 4 5 6 7 8 9 10 J Q K A 2 3 4 5 6 7 8 9 10 J Q K A 2 3 4 5 6 7 8 9 10 J Q K A

when I apply my remove command it become:

cards: 2 3 4 5 6 7 8 9 10 J Q K 2 3 4 5 6 7 8 9 10 J Q K 2 3 4 5 6 7 8 9 10 J Q K 2 3 4 5 6 7 8 9 10 J Q K

it removes all the A's from array. But I want to remove only the last item from whole array. Whats the problem how can I solve this?

In `w => w != newDeck.Last()` you are comparing strings, so all strings "A" are considered equals, that´s why all A´s are removed. (Strings are compared by value not by reference) — Daniel J.G., Nov 15 '14 at 13:19

score 105 · Accepted Answer · answered Nov 15 '14 at 13:16

105

To remove just the last element use this:

newDeck = newDeck.Take(newDeck.Count() - 1).ToArray();

Your solution removes all Elements that are equal to the last element. For a string, this means, it removes all elements equal to A

answered Nov 15 '14 at 13:16

Flat Eric

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Instead of `newDeck.Take(newDeck.Count() - 1)`, you can use `.SkipLast(1)`. – felixfbecker Sep 04 '18 at 21:50
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@felixfbecker `SkipLast()` is no standard linq method. It is implemented in 3rd party projects like `MoreLinq` – Flat Eric Sep 05 '18 at 06:01
Yes it is: https://learn.microsoft.com/en-us/dotnet/api/system.linq.enumerable.skiplast – felixfbecker Sep 05 '18 at 15:01
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@felixfbecker This is a .NET Core method. Most people still use the regular .NET Framework. – Dmytro Shevchenko Sep 09 '18 at 02:06
I just tried this method (`.Take`) versus Ahmet's method (`.Resize`) and `.Resize` is consistently faster. And I mean consistently, like I would bet a huge amount of money. The longer the array, the greater the difference. – Andrew Steitz May 15 '19 at 21:16
@DmytroShevchenko: interesting that it's in the .Net 2.0 standard... – nomen Nov 20 '19 at 23:37

Ahmet Arslan · Answer 2 · 2022-10-05T22:02:57.500

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You can use Array class to resize:

Array.Resize(ref result, result.Length - 1);

It creates a new array with a specified size and copies elements to the new array. It does not actually resize the array, naming is a bit misleading.

It is actually not possible to resize an array. Arrays are fixed collections. It is by design to keep implementations of array efficient.

edited Oct 05 '22 at 22:02

answered Apr 27 '16 at 12:41

Ahmet Arslan

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I just tried this method versus Flat Eric's method (`.Take`) and this method (`.Resize`) is consistently faster. And I mean consistently, like I would bet a huge amount of money. The longer the array, the greater the difference. – Andrew Steitz May 15 '19 at 21:15
Agreed. The speed boost is nice, too. ;-) – Andrew Steitz May 22 '19 at 19:48

score 11 · Answer 3 · answered Nov 15 '14 at 13:36

@Flat Eric explained why your solution is not working.

Here is alternate for removing last element:

newDeck = newDeck.Reverse().Skip(1).Reverse().ToArray();

Clarification:

[a, b, c] => Reverse => [c, b, a] => Skip(1) => [b, a] => Reverse() => [a, b]

score 11 · Answer 4 · answered Jan 11 '22 at 19:58

It's easy to remove the last item of an array if you're using C# 8.0 (released with .net 3.0) or above.

You can remove the last item by combining the "hat" ^ operator with the range .. operator:

newDeck = newDeck[..^1];  // all items in the array except the last

Some other examples of ^ and ..:

var lastItem   = newDeck[^1];    // last item in array
var allItems   = newDeck[..];    // all items
var skipTwo    = newDeck[2..];   // all items except the first 2 items
var innerItems = newDeck[1..^1]  // all items except the first and last

Online demo

Damn, I did not know this kind of weird thing is possible. Maybe in Kotlin or something, but C#? — Damn Vegetables, Dec 06 '22 at 03:20

Deleting Last Item from Array of String

4 Answers4