Expand an Array

Question

Expand an array to all directions by duplicating the outer elements

You will be given two inputs: an array and the expansion degree
For example if I give you [[1,2,3][4,5,6][7,8,9]] and 3, you must output:

1 1 1 1 2 3 3 3 3
1 1 1 1 2 3 3 3 3
1 1 1 1 2 3 3 3 3
1 1 1 1 2 3 3 3 3
4 4 4 4 5 6 6 6 6
7 7 7 7 8 9 9 9 9
7 7 7 7 8 9 9 9 9
7 7 7 7 8 9 9 9 9
7 7 7 7 8 9 9 9 9

As you can see the given array is in the center and all the outer elements have expanded:
1 -> 3 times up, 3 times left and also to every position of the upper left corner
2-> 3 times up
5-> is not an outer element
etc

here are some more test cases to make things clearer

Input   [[4,5,6]],0   

Output   
4 5 6


Input  [[1]],2   

Output   

1 1 1 1 1  
1 1 1 1 1   
1 1 1 1 1  
1 1 1 1 1   
1 1 1 1 1   

Input  [[1,2,3]],2  

Output  
1 1 1 2 3 3 3   
1 1 1 2 3 3 3  
1 1 1 2 3 3 3
1 1 1 2 3 3 3
1 1 1 2 3 3 3    

Input  [[1,2,3][11,22,33][111,222,333][1111,2222,3333]],1   

Output  
   1       1       2       3       3
   1       1       2       3       3
  11      11      22      33      33
 111     111     222     333     333
1111    1111    2222    3333    3333
1111    1111    2222    3333    3333

You can use as many whitespaces as you like.
But the output has to be a mXn array just like it is shown here.
You cannot output a list of lists.

This is codegolf Shortest answer on bytes wins

"You cannot output a list of lists." seems like an unnecessary output restriction to me. — Erik the Outgolfer, Oct 21, 2017 at 16:19
Probably so, because the stringize part of my answer takes 41 chars, while the "actual" part only takes 19 chars. — DELETE_ME, Oct 21, 2017 at 16:23
Test cases are not an acceptable alternative to a clear specification. — user45941, Oct 23, 2017 at 12:26

Community · Accepted Answer · 2020-06-17 09:04:33Z

4

Octave, 35 bytes

@(a,x)padarray(a,[x x],'replicate')

Try it online!

edited Jun 17, 2020 at 9:04

CommunityBot

1

answered Oct 21, 2017 at 15:59

rahnema1

5,6651 gold badge14 silver badges22 bronze badges

\$\begingroup\$ Is this a builtin in Octave? \$\endgroup\$
– Erik the Outgolfer
Oct 21, 2017 at 16:21
\$\begingroup\$ @EriktheOutgolfer It belongs to the image processing package. \$\endgroup\$
– rahnema1
Oct 21, 2017 at 16:24

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Community · Accepted Answer · 2020-06-17 09:04:33Z

4

Matlab, 27 bytes

@(a,n)padarray(a,[n,n],'r')

The key over the Octave solution is that Matlab accepts partial option strings when they are unambiguous.

edited Jun 17, 2020 at 9:04

CommunityBot

1

answered Oct 21, 2017 at 22:48

user71659

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Community · Accepted Answer · 2020-06-17 09:04:33Z

3

MATL, 10 bytes

th2Y5I4$Ya

Port of @rahnema1's Octave answer.

Try it online!

Explanation

t      % Implicit input: number, n. Duplicate
h      % Concatenate. Gives an array [n,n]
2Y5    % Push 'replicate' (predefined literal). Will be used as an input flag
I      % Push 3. Will be used as equivalent to an input flag
4$     % Specify that the next function will use 4 inputs
Ya     % Call 'padarray' with 4 inputs. This takes the array as implicit
       % input. Number 3 as third input is interpreted as the input flag 
       % 'both'. So the function pads the array (first input) by n in each
       % dimension (second input) by replicating the border (third input) in 
       % both directions (fourth input). Implicit display

edited Jun 17, 2020 at 9:04

CommunityBot

1

answered Oct 21, 2017 at 17:25

Luis Mendo

104k9 gold badges132 silver badges365 bronze badges

2

\$\begingroup\$ Explanation please? \$\endgroup\$
– Erik the Outgolfer
Oct 21, 2017 at 18:15
\$\begingroup\$ @EriktheOutgolfer Added \$\endgroup\$
– Luis Mendo
Oct 21, 2017 at 18:39

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Erik the Outgolfer · Accepted Answer · 2017-10-21 16:40:13Z

2

Jelly, 13 bytes

;ṫ¥0$¡Ṛ$⁺Zµ⁺G

Try it online!

edited Oct 21, 2017 at 16:40

answered Oct 21, 2017 at 16:27

Erik the Outgolfer

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\$\begingroup\$ I will NEVER learn how to use Jelly... \$\endgroup\$
– RedClover
Oct 21, 2017 at 16:45

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ovs · Accepted Answer · 2017-10-22 06:38:31Z

1

Python 2, 138 113 bytes

-9 bytes thanks to @JonathanFrech
-16 bytes thanks to @Lynn

a,n=input()
for e in a[:1]*n+a+n*a[-1:]:print' '.join('%*s'%(len(`max(sum(a,[]))`),n)for n in e[:1]*n+e+n*e[-1:])

Try it online!

edited Oct 22, 2017 at 6:38

answered Oct 21, 2017 at 19:15

ovs

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\$\begingroup\$ 129 bytes; using string formatting to pad the output. \$\endgroup\$
– Jonathan Frech
Oct 21, 2017 at 22:53
\$\begingroup\$ 113 bytes. \$\endgroup\$
– Lynn
Oct 22, 2017 at 2:02

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Erik the Outgolfer · Accepted Answer · 2017-10-22 17:15:00Z

1

05AB1E, 15 bytes

2F2F¤¸².×«R}ø}»

Try it online!

Yes, this output format is valid.

answered Oct 22, 2017 at 17:15

Erik the Outgolfer

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Neil · Accepted Answer · 2017-10-22 18:25:44Z

05AB1E, 33 28 23 bytes

F2Fø2FR¤¸«]øεD€gZs-ú}ø»

Try it online! 15 10 bytes of actual code, the rest is formatting the output. Explanation:

       ¤                Copy last element
        ¸               Turn it into a list
         «              Concatenate
    2F                  Repeat twice
      R                 Reverse list each time
 2F                     Repeat twice
   ø                    Transpose list each time
F                       Repeat the given number of times
          ]             Close all the loops
           ø            Transpose the array
             D          Duplicate
              €g        Take length of each number
                Z       Get the maximum
                 s-     Subtract each length from the maximum
                   ú    Pad with that number of spaces
            ε       }   For each row (column originally)
                     ø  Transpose back
                      » Join with spaces and newlines

Formatting costs 2 bytes if I copy @ErikTheOutgolfer's output format for 12 bytes:

F2Fø2FR¤¸«]»

agtoever · Accepted Answer · 2017-10-22 21:24:33Z

0

Python 2.7, 74 characters

Pretty straightforward: uses numpy padding and regex to force a return string without brackets. This code returns an anonymous lambda.

import numpy,re;lambda a,n:re.sub('[\[\]]', '',str(numpy.pad(a,n,'edge')))

answered Oct 22, 2017 at 21:24

agtoever

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TFeld · Accepted Answer · 2017-10-23 12:02:01Z

0

Python 2, 94 89 86 82 bytes

a,n=input()
for l in a[:1]*n+a+n*a[-1:]:print' '.join(map(str,l[:1]*n+l+n*l[-1:]))

Try it online!

edited Oct 23, 2017 at 12:02

answered Oct 23, 2017 at 10:41

TFeld

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Stack Exchange Network

Expand an Array

9 Answers 9

Octave, 35 bytes

Matlab, 27 bytes

MATL, 10 bytes

Explanation

Jelly, 13 bytes

Python 2, 138 113 bytes

05AB1E, 15 bytes

05AB1E, 33 28 23 bytes

Python 2.7, 74 characters

Python 2, 94 89 86 82 bytes

Your Answer

Hot Network Questions

Expand an Array

9 Answers 9

Octave, 35 bytes

Matlab, 27 bytes

MATL, 10 bytes

Explanation

Jelly, 13 bytes

Python 2, 138 113 bytes

05AB1E, 15 bytes

05AB1E, 33 28 23 bytes

Python 2.7, 74 characters

Python 2, 94 89 86 82 bytes

Your Answer

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