Create chunks from an array

Question

Your task is to write a program which given an array and a number, you need to split the array into chunks with size is number.

Rules

Your program will receive an array A , as well as a positive integer n. The array should then be split into chunks of length n, if the length of the string isn't divisible by n any leftover at the end should be considered its own chunk.

• If n is greater than length of array A, you will need to return array A, for example: if n = 4 and array A = [1,2,3], you should return [1,2,3]

• The array can contain any type rather than number.

• You should not change order (or direction) of any item from left to right. For example if n = 2 and A= [1,2,3]. Any result rather than [[1,2],[3]] will be invalid.

Test Cases

n A Output
2 [1,2,3,4,5,6] [[1,2],[3,4],[5,6]]
3 [1,2,3,4,5,6] [[1,2,3],[4,5,6]]
4 [1,2,3,4,5,6] [[1,2,3,4],[5,6]]

This is code-golf, so you the shortest bytes of each language will be the winner.

• Adám: If n is greater than the length of A we need to return A‽ Are you sure you don't mean [A]?
• Adám: @chaugiang I still think a too large n should return [A], e.g [[1,2,3]]. What if n is exactly the length of A?
• Jonah: @chaugiang Adam is correct imo. The return value should be consistent.
• DJMcMayhem: @chaugiang Can n ever equal 1?
• dfeuer: In a strongly typed language, it's simply impossible to return A rather than [A] , which would exclude an awful lot of languages.

Answer 1

05AB1E, 1 byte

ô

Try it online or verify all test cases.

Builtins ftw. :)

Answer 2

JavaScript (ES6), 36 bytes

Takes input as (n)(array).

n=>g=a=>a+a&&[a.splice(0,n),...g(a)]

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Commented

n => // n = chunk size
 g = a => // g = recursive function taking the array a[]
 a + a // if a[] is empty, stop recursion and return an empty string
 && // otherwise, return an array made of:
 [ a.splice(0, n), // the next chunk
 ...g(a) // followed by the result of a recursive call
 ] // (the last call leads to ...'', which adds nothing)

• Joe the Person: Now that is a neat and clean solution, and I learned about recursive anonymous functions too!

Answer 3

APL (Dyalog Unicode), 12 bytes ^SBCS

⊢⊂⍨(⍴⊢)⍴1↑⍨⊣

Big thanks to Adám for basically doing basically all the golfing (and for basically all the APL knowledge I have currently>_>).

Explanation

 ⊂⍨ Partitioned enclose (commuted, i.e. left and right switched) - for each ⍵ in left, ⍺ in right, if ⍺ = 0, create a new sub-array, push ⍵ to latest sub-array
⊢ Right argument of entire expression
 ⍴ Reshape - Change size of right into dimensions specified by left
 (⍴ ) Shape of (here, there is only one dimension - length)
 ⊢ Right argument of entire expression
 ↑⍨ Take (commuted) - takes ⍺ elements from left where ⍺ is right. Extra elements (zeroes here) are automatically added
 1 1
 ⊣ Left argument of entire expression

Execution

Arguments 2, 1 2 3 4 5 6 7. Note that APL arrays are of the form a b c, with optional surrounding parentheses.

 ⊣ 2
 1 1
 ↑⍨ 1↑2 = 1 0
 ⊢ 1 2 3 4 5 6 7
 (⍴ ) ⍴1 2 3 4 5 6 7 =わ 7
 ⍴ 7⍴1 0 =わ 1 0 1 0 1 0 1
⊢ 1 2 3 4 5 6 7
 ⊂⍨ 1 0 1 0 1 0 1⊂1 2 3 4 5 6 7 = (1 2)(3 4)(5 6)(7)

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• Adám: Congratulations on your first APL answer. And nicely explained too! Here, have an APL pie: 🥧

Answer 4

Python 3, 61 bytes

lambda A,n:[A,[A[x:x+n]for x in range(0,len(A),n)]][n<len(A)]

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Modifies Henry T's existing Python 3 solution to produce valid output for n>= len(A).
Posting as its own answer due to lack of commenting privileges.

Answer 5

Prolog (SWI), (削除) 90 (削除ここまで) (削除) 84 (削除ここまで) 61 bytes

Code:

[]*_*[].
L*N*[P|R]:-length(P,N),append(P,T,L),T*N*R;P=L,R=[].

The input format might be a bit weird, but it is:

A * n * Result.

For example, for the input:

n = 2
A = [1, 2, 3, 4, 5, 6]

You would need to use [1, 2, 3, 4, 5, 6] * 2 * Result..

Try it online!

Ungolfed version:

divide([], _, []).
divide(List, N, [Prefix | Result]) :-
 length(Prefix, N), append(Prefix, Remaining, List), divide(Remaining, N, Result) 
 ; Prefix = List, Result = [].

Try it online!.

Answer 6

Perl 6, 13 bytes

{*.batch($_)}

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Curried function wrapping the batch built-in.

• Jo King: Did they fix that bug where you had to have a ; after the Whatever code?
• nwellnhof: @JoKing No. You only need a ; when passing arguments with $^a or @_.

Answer 7

Clean, 54 bytes

import StdEnv
$n l=[l%(i,i+n-1)\\i<-[0,n..length l-1]]

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Answer 8

PHP, 15 bytes

$f=array_chunk;

requires PHP 7. Call with $f(ARRAY, N).

• Neil: I don't think you're required to give another name to a builtin, so this just scores 11, doesn't it?
• Titus: @Neil I thought that might be a forbidden loophole; but you may be right.

Answer 9

Python 2, 39 bytes

i,j=input()
while j:print j[:i];j=j[i:]

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Assumes that 1 chunk per line is acceptable output.

• ovs: 36 bytes as a recursive lambda function
• ElPedro: @ovs - Very nice and also different enough for you to post as your own answer if you wish.

Answer 10

Brainfuck, 71 bytes

,[>+>+<<-]>>>,[<[>.,<-]>>>++++[<++++++++>-]<.[-]<<<[<+>>+<-]<[->+<]>>>]

Dunno if this counts or not... input format:

<character whose ascii is n>AAAAAAAAAAAAA
For example, in the input:
 1234567890123492034
n is 32 since the ASCII value of space is 32

Takes the input and puts in a space every time n characters pass

Explanation (no commas because that would break the program):

, take n
[>+>+<<-] copy into next two cells (destroys original)
>>>, take first of A into next cell
[ while that input exists
<[>.,<-] if n is nonzero output take next of A subtract one from n
>>>++++[<++++++++>-]<.[-]< n is zero so put a space
<<[<+>>+<-] copy the old n into surrounding cells
<[->+<] move from first cell to second
>>>] take input, do again

• MilkyWay90: Remove the spaces for 71 characters
• willowis.cool: lol, I thought I removed all of them but I didn't notice those, thanks!
• MilkyWay90: Try reorganizing the cells such that the cells you use more are more accessible (for example, if the input cell (the one where you use , more) is used more it could be put an a cell which is easier to access than if it was placed in other cells) or use a bruteforcer. I am not skilled in golfing in BF so these suggestions may not be helpful.
• willowis.cool: So far I have n n n A space as my cell setup, if you can think of a better way...
• MilkyWay90: Could A space n n n ... work (or space A n n n...)?

Answer 11

Python 3, 46 chars

lambda A,n:[A[:n],*(f(A[n:],n)if A[n:]else[])]

-1 thanks to @Collin Phillips.

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• Collin Phillips: I was able to get it to 46 characters with recursion

Answer 12

CJam, 3 bytes

{/}

This is an anonymous block that takes an array of numbers and a number from the stack, and replaces them by an array of arrays.

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Answer 13

Brachylog, 2 bytes

ġ)

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• Kroppeb: I read the statement, This came to mind immediately =). #builtinsFTW

Answer 14

Elixir, 16 bytes

Enum.chunk_every

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Answer 15

Charcoal, 1 byte

⪪

Try it online! Charcoal's default I/O makes it difficult to demonstrate using anything except strings. If you want a full program that takes numeric lists and outputs formatted lists then this can be done as follows:

E⪪AN⪫ι,

Try it online! Link is to verbose version of code. Explanation:

 A Input array
 ⪪ Split into chunks of
 N Input number
E Map over chunks
 ι Current chunk
 ⪫ Joined with
 , Literal `,`
 Implicitly print each chunk on its own line

Answer 16

C# (Visual C# Interactive Compiler), (削除) 78 (削除ここまで) (削除) 77 (削除ここまで) 43 bytes

a=>b=>{int i=0;return a.GroupBy(_=>i++/b);}

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I think we should be able to just write int i; because 0 is the default of int. I let it to avoid the error: error CS0165: Use of unassigned local variable 'i'.

Answer 17

F# (.NET Core), 15 bytes

Seq.chunkBySize

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Well F# has a builtin...

Answer 18

J, 4 bytes

<\~-

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Takes the array as left arg and chunk size as right arg.

Uses a dyadic hook and the infix adverb with a negative argument, which does what we want by definition.

Note: The return type must be boxed because J only allows tables of equal sized items.

Answer 19

Japt, 2 bytes

òV

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Answer 20

PHP, 45 bytes

function f($a,$b){return array_chunk($a,$b);}

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• Arnauld: Would just array_chunk be a valid answer?
• Luis felipe De jesus Munoz: @Arnauld I dont know. Never golfed in php before although I use it at work.
• Arnauld: I'm not 100% sure either, but we can abuse the implicit conversion of undeclared variables to a string and do something like that.
• Arnauld: (erratum: I meant undefined constants)

Answer 21

Java 10, (削除) 106 (削除ここまで) 80 bytes

L->n->{for(int l=L.size(),i=0;i<l;)System.out.print(L.subList(i,(i+=n)<l?i:l));}

Prints the chunks without delimiter.

Try it online.

106 bytes:

L->n->{var r=new java.util.Stack();for(int l=L.size(),i=0;i<l;)r.add(L.subList(i,(i+=n)<l?i:l));return r;}

Actually returns a list of lists.

Try it online.

Explanation:

L->n->{ // Method with List and integer parameters and List return-type
 var r=new java.util.Stack();// Create an empty List
 for(int l=L.size(), // Determine the size of the input-List
 i=0;i<l;) // Loop `i` in the range [0, size):
 r.add( // Add to the result-List:
 L.subList(i, // A sublist of the input-list in the range from `i`
 Math.min(i+=n,l))); // to the minimum of: `i` + input-integer or the size
 // (and increase `i` by the input-integer at the same)
 return r;} // Return the List of Lists of integers as result

Answer 22

K (oK), 10 bytes

{(0N,x)#y}

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Answer 23

Ruby, 25 bytes

->n,a{[*a.each_slice(n)]}

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If we can return enumerators instead of arrays, then it becomes simply:

Ruby, 21 bytes

->n,a{a.each_slice n}

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Answer 24

PicoLisp, (削除) 75 (削除ここまで) 74 bytes

(de f(n l)(if(>= n(length l))(list l)(cons(head n l)(f n(tail(- 0 n)l)))))

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Answer 25

Coconut, 8 bytes

groupsof

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Answer 26

V, 6 bytes

òÀf,r

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Hexdump:

00000000: f2c0 662c 720a ..f,r.

Explanation:

ò " Until an error happens:
 f " (f)ind the...
 À " n'th...
 , " ","
 " (If there are less than n commas after the cursor, throw an error)
 r " Replace the char under the cursor with...
 <cr> " A newline

Answer 27

Clojure, 14 bytes

#(partition %)

builtins I guess

• NikoNyrh: Hi, welcome. The function should take two arguments: the array to be partitioned and the length of the chunk. Also what happens if the last chunk isn't "full" when using partition?

Answer 28

Haskell, 26 bytes

import Data.Lists
chunksOf

Here's a more interesting version, with just a few more bytes (thanks to nimi for five bytes in each solution):

Haskell, 31 bytes

n![]=[]
n!x=take n x:n!drop n x

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• aloisdg: I think you can
• nimi: n!x=take n x:n!drop n x. Data.Lists provides also chunksOf.

Answer 29

PowerShell, (削除) 67 (削除ここまで) 65 bytes

-2 bytes thanks AdmBorkBork

param($n,$a)$a|%{$b+=,$_
if($b.Count-ge$n){,$b;rv b}}
if($b){,$b}

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• AdmBorkBork: You should be able to rv b (alias for Remove-Variable) instead of $b=@() to save two bytes.

Answer 30

R, (削除) 49 (削除ここまで) 36 bytes

function(A,n)split(A,(seq(A)-1)%/%n)

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Thanks to Kirill L. for the golf.

• Kirill L.: How about this, for 36
• Giuseppe: @KirillL. of course. Thanks!