16
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Given a string, you've to split it into groups of three characters (by padding _ at the end).

Related, but still it's different.


Sample I/O:

  • 'abcde' -> 'abc', 'de_'

  • '1234' -> '123', '4__'

  • '' -> [] or falsey value

  • 'Three spree!' -> 'Thr', 'ee ', 'spr', 'ee!'

  • 6 MB string

This is a , so fewest bytes will win!

Edit: Finally, output is unrestricted.

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  • 10
    \$\begingroup\$ Why special case the empty string? May we choose which character to use for the padding? \$\endgroup\$ – Shaggy May 19 '19 at 14:49
  • 12
    \$\begingroup\$ So the task is actually: Given a string, return a falsey value if it is empty, otherwise split it into groups of three, padding with underscores if necessary? Seems like an odd pair-up of two unrelated tasks (checking string length and splitting). \$\endgroup\$ – Adám May 19 '19 at 15:27
  • 15
    \$\begingroup\$ Things to avoid: Exceptional edge cases. In this case, an empty string should returnan empty array or equivalent, not a falsey value \$\endgroup\$ – Jo King May 19 '19 at 22:05
  • 6
    \$\begingroup\$ Lots of statically-typed languages cannot return more than one type from a function \$\endgroup\$ – Embodiment of Ignorance May 19 '19 at 23:30
  • 4
    \$\begingroup\$ @manassehkatz Yes, but only in those languages. In some languages it makes solutions far more complicated, or even impossible (e.g statically typed languages). \$\endgroup\$ – Jo King May 20 '19 at 22:01

38 Answers 38

10
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05AB1E, 9 8 bytes

…___«3ô¨

Try it online! or as a Test Suite

Explanation

…___«      # append "___" to input
     3ô    # split into groups of 3
       ¨   # discard the last group
|improve this answer|||||
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8
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Python 3, 58 47 34 bytes

I'm sure someone else can do better Someone else did better. Thanks Jo King for -11 -24 bytes!

Output is unrestricted, welcome to tuple hell. Returns empty list (falsy) on empty input

lambda x:[*zip(*[iter(x+"__")]*3)]

TIO

|improve this answer|||||
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6
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JavaScript, 25 bytes

s=>`${s}__`.match(/.../g)

Try it

|improve this answer|||||
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5
\$\begingroup\$

Perl 5, 16 15 bytes

"@_\__"=~/.../g

Try it online!

|improve this answer|||||
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  • 1
    \$\begingroup\$ 15 with "@_\__"=~/.../g. There were other 16s: (pop.__)=~/.../g or map/.../g,pop.__. \$\endgroup\$ – Grimmy May 20 '19 at 11:50
  • 1
    \$\begingroup\$ Thx to @Grimy for the tip on \. It shaved off 1 byte and I learned something new. \$\endgroup\$ – Kjetil S. May 20 '19 at 13:30
4
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APL+WIN 36 24 22 bytes

12 bytes saved as a result of output now being de-restricted and using the code in @Adám's first comment modified to work in APL+WIN and a further 2 with his second comment. Thanks.

(⌈(↑⍴s)÷3)3⍴(s←⎕),'__'

Prompts for input of the string and outputs the result as a nx3 array

Try it online! Courtesy of Dyalog Classic

|improve this answer|||||
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  • \$\begingroup\$ @Adám. Throws a domain error in APL+WIN at the right most ⍴ \$\endgroup\$ – Graham May 19 '19 at 13:45
  • \$\begingroup\$ Fails on '', no? I think OP (for some strange reason) requires the result to be 0 (with any rank). \$\endgroup\$ – Adám May 19 '19 at 15:47
  • 1
    \$\begingroup\$ @Adám It produces a 0 x 3 array. The OP now appears to want "falsey" for a null input. With the spec keeping on changing I am going to bow out at this point and leave my answer as its stands! Thanks for your improvements. \$\endgroup\$ – Graham May 19 '19 at 16:12
4
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JavaScript, 51 50 48 27 25

b=>(b+"__").match(/.../g)

Try it online!

|improve this answer|||||
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  • \$\begingroup\$ Welcome to PPCG! :) But ... codegolf.stackexchange.com/a/185808/58974 \$\endgroup\$ – Shaggy May 24 '19 at 16:51
  • \$\begingroup\$ @Shaggy I didn't even see that ¯\_(ツ)_/¯ \$\endgroup\$ – VFDan May 24 '19 at 17:21
  • \$\begingroup\$ No worries, it happens. \$\endgroup\$ – Shaggy May 24 '19 at 17:24
3
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Perl 6, 19 bytes

{$_~"__"~~m:g/.../}

Try it online!

Pads the string by two underscores then splits the string into chunks of three characters. Returns as an array of Match objects.

|improve this answer|||||
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3
\$\begingroup\$

Japt, 8 bytes

+1 byte to special case the empty string. Can save 2 if we can choose our padding character.

©ò3 ú'_3

Try it

©ò3 ú'_3     :Implicit input of string
©            :Logical AND with
 ò3          :Split into chunks of 3
    ú'_3     :Right pad each with "_" to length 3
|improve this answer|||||
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2
\$\begingroup\$

Stax, 7 bytes

é☻εgP▀╪

Run and debug it

For an empty string input, the result is an empty array, which is a falsey value in stax.

|improve this answer|||||
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2
\$\begingroup\$

CJam, 11 bytes

q'_3*+3/);p

Try it online!

For empty input this gives an empty string, which is falsy.

How it works

q     e# Read input as a string
'_    e# Push char '_'
3*    e# String formed by that char repeated 3 times
+     e# Concatenate to input string
3/    e# Split in groups of 3, the last of which may be shorter. Gives array of strings
);    e# Detach last string from the array and delete it
p     e# Print string representation of the array
|improve this answer|||||
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2
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Retina 0.8.2, 10 bytes

$
__
!`...

Try it online! Link includes test cases. Explanation:

$
__

Append two _s, in case the last group needs to be padded.

!`...

Match as many groups of three as possible, outputting the matches themselves rather than the count. (In Retina 1 this would be L instead of !.)

|improve this answer|||||
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2
\$\begingroup\$

C (gcc), 67 bytes

i;f(char*_){for(;*_;puts(""))for(i=3;i--;)putchar(*_?*_++:95);_=0;}

Try it online!

Always returns a falsey value (0).

|improve this answer|||||
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  • 2
    \$\begingroup\$ Do you even need to return anything? \$\endgroup\$ – ceilingcat May 20 '19 at 14:11
  • \$\begingroup\$ 63 bytes \$\endgroup\$ – Johan du Toit May 21 '19 at 10:28
2
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Wolfram Language (Mathematica), 28 21 bytes

-7: No longer requires falsy (False) value on empty input

Partition[#,3,1,1,_]&

Try it online!

Takes a list of characters as input. Returns a list of 3-tuples of characters padded with Blanks (_).


34 27 bytes

StringPartition[#<>"__",3]&

Try it online!

String input, list of strings output

|improve this answer|||||
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1
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Jelly, 9 bytes

s3o€“___”

A monadic Link accepting a list of characters which yields a list of lists of characters (an empty input yields empty output).

Try it online!

How?

s3o€“___” - Link: list of characters
s3        - split into chunks of three
   €      - for each chunk:
  o       -   OR (vectorises):
    “___” -     list of characters = ['_', '_', '_']

Notes:
The is only necessary to handle the edge case of an empty input.
A full program can drop a trailing , but here we can't do that as the printing behaviour of a full program smashes everything together.


Equivalent 9:

o3ÐƤ“___”

Try it


Alternative 9:

;“___”s3Ṗ

Try it

|improve this answer|||||
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1
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J, 16 bytes

[:}:_3]\'___',~]

Try it online!

K (oK), 19 17 bytes

-2 bytes thanks to ngn!

{-1_0N 3#x,"___"}

Try it online!

|improve this answer|||||
\$\endgroup\$
  • 1
    \$\begingroup\$ k: (0N;3) -> 0N 3 \$\endgroup\$ – ngn May 20 '19 at 7:21
  • \$\begingroup\$ @ngn Thank you! \$\endgroup\$ – Galen Ivanov May 20 '19 at 7:28
1
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Java 10, 116 113 bytes

s->{s+="__";int l=s.length()/3,i=l;var r=new String[l];for(;i-->0;)r[i]=s.substring(i*3,i*3+3);return l<1?0>1:r;}

Try it online.

Or 104 101 bytes if an empty array instead of false is allowed as output..

s->{s+="__";int l=s.length()/3;var r=new String[l];for(;l-->0;)r[l]=s.substring(l*3,l*3+3);return r;}

Try it online.

Explanation:

s->{                             // Method with String as both parameter and return-type
  s+="__";                       //  Append two "_" to the input-String
  int l=s.length()/3;            //  Get the length, integer-divided by 3
  var r=new String[l];           //  Create a string-array with that many parts
  for(;l-->0;)                   //  Loop `l` in the range (l, 0]:
    r[l]=                        //   Set the `l`'th value of the array to:
         s.substring(l*3,l*3+3); //   Get the substring of size 3 from index `l*3` from `s`
  return r;}                     //  Return the array
|improve this answer|||||
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  • \$\begingroup\$ An empty array is now allowed \$\endgroup\$ – Benjamin Urquhart May 26 '19 at 3:57
1
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Ruby, 73 42 bytes

a=gets
a.length!=0?a.scan(/.{1,3}/).map{|s|(s+'_'*3)[0,3]}:'falsey value'

Edit: As falsey value looks like it's not required:

gets.scan(/.{1,3}/).map{|s|(s+'_'*3)[0,3]}
|improve this answer|||||
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  • 1
    \$\begingroup\$ The maximum padding is of 2 characters, so '_'*2 would be enough, for which a literal '__' is shorter. But if you add the padding in advance then simply not match the pieces shorter than 3 characters, is shorter: puts"#{gets}__".scan /.../. (Note that without the explicit printing that is considered irb not ruby.) \$\endgroup\$ – manatwork May 20 '19 at 15:06
1
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C# (Visual C# Interactive Compiler), 74 bytes

Just append two underscores '_' at the end of the input to make sure they get printed if the length of the input isn't a factor of 3.

s=>Enumerable.Range(0,(s.Length+2)/3).Select(i=>(s+"__").Substring(i*3,3))

Try it online!

|improve this answer|||||
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1
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Kotlin, 34 bytes

{"${it}__".chunked(3).dropLast(1)}

Try it online!

|improve this answer|||||
\$\endgroup\$
  • \$\begingroup\$ this does not work, try {"${it}___".chunked(3).dropLast(1)} \$\endgroup\$ – pme May 21 '19 at 6:45
1
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C (gcc), 55 bytes

i;f(char*s){for(;i%4|*s;)putchar(++i%4?*s?*s++:95:10);}

Try it online!

|improve this answer|||||
\$\endgroup\$
  • \$\begingroup\$ Using 9(\t) instead of 10(\n) should be fine, but that's not main point \$\endgroup\$ – l4m2 May 20 '19 at 15:23
1
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C (clang), 128 126 94 67 bytes

67 bytes thanks to @ceilingcat

f(char*k){for(;*k;k++)printf("%c%c%c\n",*k,*++k?*k:95,*++k?*k:95);}

Try it online!

|improve this answer|||||
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1
\$\begingroup\$

Bash, 90 bytes

This uses Bash features rather than a combination of more traditional Bourne shell plus *nix commands (which one version I created ended up at 205 bytes). I cheated by using the dodge of adding two _ characters to the string.

c=;read a;a=${a}__;while (($(echo ${#a})>2));do b=${a:0:3};c=$c\ $b;a=${a#$b};done;echo $c

Try it online!

|improve this answer|||||
\$\endgroup\$
1
\$\begingroup\$

PowerShell, 58 35 bytes

$args-split'(...)'-ne''|% *ht 3 '_'

-23 bytes thanks to mazzy.

Try it online!

|improve this answer|||||
\$\endgroup\$
  • \$\begingroup\$ Nice. 1) You can count a code that can be extracted into a ps1-file and executed. 2) See shortcuts. 3) Try to golf more \$\endgroup\$ – mazzy May 25 '19 at 5:18
1
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GNU sed, 27 bytes

s:$:__:
s:...:& :g
s: _*$::

Try it online!

It gets a bit tricky regarding the empty string input, since sed has no meaning of a falsy value. So to deal with this, I provide you with two possible interpretations of the rules to validate my submission:


A. You essentially provide nothing as input, not even a trailing newline (as it is the case with all the examples, including that 6 Mb file).

Usage:

echo -n ""|sed -f script

Output: nothing is printed, because sed doesn't even run the script without input.


B. One could consider as falsy value for sed to be an unique string, i.e., returned only when the input is an empty string.

Usage:

echo ""|sed -f script

Output:

__

I prefer the first interpretation so much more, as I believe it to be the closest to the intended rule, but the last one helps if you run the script using that TIO link.

|improve this answer|||||
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0
\$\begingroup\$

JavaScript (Babel Node), 45 bytes

_=>_.match(/.{1,3}/g).map(a=>a.padEnd(3,`_`))

Try it online!

|improve this answer|||||
\$\endgroup\$
  • \$\begingroup\$ 44 \$\endgroup\$ – Shaggy May 19 '19 at 15:13
  • \$\begingroup\$ Doesn't work for me \$\endgroup\$ – VFDan May 22 '19 at 21:55
0
\$\begingroup\$

Jelly, 10 bytes

s3;€⁾__ḣ€3

Try it online!

It feels like an 8 or 9 should be possible, but haven’t found one yet.

|improve this answer|||||
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0
\$\begingroup\$

Attache, 34 23 bytes

PadRight&"_"&3=>@Chop&3

Try it online!

Explanation (outdated)

{On[#_-1,PadRight&"_"&3,_]}@Chop&3
                           @Chop&3    chop the input string into groups of 3s
{On[#_-1               ,_]}           on the last group
        ,PadRight                         pad it
                     &3                   to length three
                 &"_"                     with underscores
|improve this answer|||||
\$\endgroup\$
  • \$\begingroup\$ Would you save anything by padding all the elements instead of just the last one? \$\endgroup\$ – Shaggy May 19 '19 at 20:18
  • \$\begingroup\$ @Shaggy Good point! I’ll look into it \$\endgroup\$ – Conor O'Brien May 19 '19 at 20:19
0
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Charcoal, 10 bytes

E⪪S³…⁺ι__³

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

  S         Input string
 ⪪ ³        Split into groups of up to 3 characters
E           Map over each group
      ι     Current group
     ⁺      Concatenated with
       __   Literal `__`
    …    ³  Moulded to length 3
            Each group implicitly printed on its own line
|improve this answer|||||
\$\endgroup\$
0
\$\begingroup\$

Scala, 31 bytes

(s+"___").grouped(3).toSeq.init

Try it online!

Explanation

(s+"___")       // add "___"
  .grouped(3)   // make groups of 3
  .toSeq        // change to Seq
  .init         // take all but last
|improve this answer|||||
\$\endgroup\$
  • \$\begingroup\$ You'll have to add some part of the function definition in, otherwise you won't know where s is coming from \$\endgroup\$ – Jo King Mar 26 at 10:17
0
\$\begingroup\$

Befunge-93, 30 29 bytes

~:1+%,~:1+!"`"*+,~:1+!"`"*+,,

Try it online!

Outputs nothing for an empty input, otherwise outputs strings of length 3 separated by NUL characters.

Explanation:

~                               Push character of input to stack
 :1+                            Duplicate input and add 1
    %                           Modulo top 2 values of stack and push result
                                If input was -1 (end of stream), calculate -1%0 -> halt
                                Otherwise calculate input%(input+1) -> input
     ,                          Pop and output character
      ~                         Push character of input to stack
       :1+!                     Duplicate input, add 1 and perform logical NOT
           "`"*                 Multiply by 96 (ASCII code for '`')
                                This returns 96 or 0 depending on the result of the NOT
               +                Add the top 2 values from the stack and push the result
                                If the input was -1 (end of stream), pushes -1+96=95, or the ASCII code for '_'
                                Otherwise pushes input+0
                ,               Pop and output character
                 ~:1+!"`"*+,    Same block again to handle the third character
                            ,   Output a NUL character (stack is empty, so popping from stack just returns 0)

The instruction pointer wraps around at the end, looping the entire line.
|improve this answer|||||
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