Certa vez, tive uma bela matriz retangular. Era muito simétrico, mas infelizmente desmoronou e agora só tenho o canto superior esquerdo. Sua tarefa será reconstruir a matriz original.

Seu programa receberá uma matriz bidimensional de números inteiros. Para facilitar a análise, você pode assumir que todos estão entre 1 e 9. Sua tarefa é inverter as colunas da matriz, suas linhas e ambas, costurar os cantos resultantes e retornar a matriz resultante.

Você pode assumir que as dimensões da matriz serão pelo menos 1x1.

Casos de teste:

Input:
1 2 3
4 5 6

Output:
1 2 3 3 2 1
4 5 6 6 5 4
4 5 6 6 5 4
1 2 3 3 2 1

Input:
1

Output:
1 1
1 1

Input:
9
9
9

Output:
9 9
9 9
9 9
9 9
9 9
9 9

Isso é código-golfe , o menor número de bytes vence!

Próton , 29 bytes

a=>[b+b[by-1]for b:a+a[by-1]]

Experimente online!

Existem algumas outras abordagens interessantes:

Próton , 29 bytes

a=>map(g,(g=x=>x+x[by-1])(a))

Experimente online!

Você pode definir a subfunção de espelho gin-line, porque Proton. Não é mais curto.

Próton , 36 bytes

(a=>[x[0]for x:zip(*(a+a[by-1]))])*2

Experimente online!

This should be (a=>zip(*(a+a[by-1])))*2 which is 24 bytes, but the zip function is completely broken. Basically, you mirror it and zip, and then do that twice (you can multiply a function by a positive integer to apply the function multiple times).

Canvas, 1 byte

╬

Try it here!

Outputs as a multiline string

Haskell, 25 24 bytes

r=(++)<*>reverse
r.map r

Try it online!

Python 3, 38 bytes

lambda a:[b+b[::-1]for b in a+a[::-1]]

Try it online!

Takes a list of lists and returns a list of lists.

Explanation:

lambda a:                              # anonymous lambda function
                   for b in a+a[::-1]  # for each row in the array and the upside-down array
          b+b[::-1]                    # the row with its reverse appended
         [                           ] # return in a list

Husk,  7  6 bytes

Coincidentally, Erik had posted the exact same code in the Husk chatroom about a minute before I posted this.

‼oTS+↔

Try it online!

Pervious version, 7 bytes:

mS+↔S+↔

Retina, 13 bytes

\%`$
$^$`
Vs`

Try it online!

Explanation

\%`$
$^$`

On each line (%), match the end of the line ($), and insert the reverse ($^) of the entire line ($`) and print the result with a trailing linefeed (\). This does the reflection along the vertical axis and prints the first half of the output.

Vs`

This just reverses the entire string, which is equivalent to a 180° degree rotation, or in our case (due to the horizontal symmetry) a reflection along the horizontal axis. This way this works is that V's (reverse) default regex is (?m:^.*$), which normally matches each line of the string. However, we activate the singleline option s, which makes . match linefeeds as well and therefore this default regex actually matches the entire string.

The result of this is printed automatically at the end of the program, giving us the second half of the output.

05AB1E, 2 bytes

∞∊

Try it online!

   # Input:Array of String | ['12','34']
---#-----------------------+------------------------------------------
∞  # Mirror horizontally.  | [12,34]       -> [1221,3443]
 ∊ # Mirror vertically.    | [1221,3443]   -> [1221\n3443\n3443\n1221]

Credit for Mr. Xcoder pointing out that arrays of string may count as 2D arrays and Pavel for confirming it.

Jelly, 5 bytes

m€0m0

Try it online!

MATL, 5 bytes

,tPv!

Try it online!

Explanation:

(implicit input)
,               # do twice:
 t              # dup top of stack
 P              # flip vertically
 v              # vertically concatenate
 !              # transpose
(implicit output)

Octave,  33  29 bytes

Thanks to @Giuseppe for golfing four bytes!

@(A)[B=[A;flip(A)] fliplr(B)]

Try it online!

JavaScript (Node.js), 62 55 49 46 bytes

A=>(j=x=>[...x,...[...x].reverse()])(A).map(j)

Try it online!

Because Array.prototype.reverse() reverses the array in place, I have to make a shallow copy somewhere first. A=>(j=x=>[...x,...x.reverse()])(A).map(j) does not work.

J, 12 bytes

(,|.)@,.|."1

Try it online!

Explanation

         |."1 - reverse each row
       ,.     - and stitch them to the input
 (   )@       - and 
  ,|.         - append the rows in reversed order        

awk, 88 bytes

{s="";for(i=NF;i>0;i--)s=" "$i s" "$i;a[FNR]=s;print s}END{for(i=NR;i>0;i--)print a[i]}

Triangularity, 31 bytes

...)...
..IEM..
.DRs+}.
DRs+...

Try it online!

Explanation

Removing the characters that make up for the padding, here is what the program does:

)IEMDRs+}DRs+ – Full program. Takes a matrix as a 2D list from STDIN.
)             – Push a 0 onto the stack.
 I            – Take the input at that index.
  E           – Evaluate it.
   M    }     – For each row...
    DR        – Duplicate and replace the second copy by its reverse.
      s+      – Swap and append.
         DR   – Duplicate the result and replace the second copy by its reverse.
           s+ – Swap and append.

R, 57 bytes

function(m)rbind(N<-cbind(m,m[,ncol(m):1]),N[nrow(N):1,])

Try it online!

APL+WIN, 11 bytes

Prompts for a 2d array of integers.

m⍪⊖m←m,⌽m←⎕

Stax, 5 bytes

:mm:m

Run and debug it online

:m means mirror, which is input.concat(reverse(input)). m, in this context means output each line after applying...

So, mirror the array of rows, and then mirror each row and output.

Japt, 6 bytes

mê1 ê1

Try it here

Explanation

           :Implicit input of 2D array
m          :Map
 ê1        :  Mirror sub array
    ê1     :Mirror main array

Mathematica, 29 bytes

(g=#~Join~Reverse@#&)@*Map[g]

Try it online!

SOGL V0.12, 2 bytes

-1 byte thanks to dzaima.

╬ø

Try it here!

APL (Dyalog Classic), 7 bytes

⍪∘⊖⍨⊢,⌽

Try it online!

Ruby, 35 bytes

->a{r=->b{b+b.reverse}
r[a].map &r}

Try it online!

A lambda accepting a 2D array and returning a 2D array. It's straightforward, but here's the ungolfed version anyway:

->a{
  r=->b{ b+b.reverse } # r is a lambda that returns the argument and its reverse
  r[a].map &r          # Add the array's reverse, then add each row's reverse
}

Java 8, 140 131 bytes

m->{String r="";for(int a=m.length,b=m[0].length,i=a+a,j;i-->0;r+="\n")for(j=b+b;j-->0;)r+=m[i<a?i:a+a+~i][j<b?j:b+b+~j];return r;}

Explanation:

Try it online.

m->{                      // Method with integer-matrix parameter and String return-type
  String r="";            //  Result-String, starting empty
  for(int a=m.length,     //  Amount of rows of the input-matrix
          b=m[0].length,  //  Amount of columns of the input-matrix
          i=a+a,j;        //  Index integers
      i-->0;              //  Loop over double the rows
      r+="\n")            //    After every iteration: append a new-line to the result
     for(j=b+b;j-->0;)    //   Inner loop over double the columns
       r+=                //    Append the result with:
          m[i<a?          //     If `i` is smaller than the amount of rows
             i            //      Use `i` as index in the input-matrix
            :             //     Else:
             a+a+~i]      //      Use `a+a+i-1` as index instead
           [j<b?          //     If `j` is smaller than the amount of columns
             j            //      Use `j` as index in the input-matrix
            :             //     Else:
             b+b+~j];     //      Use `b+b+j-1` as index instead
  return r;}              //  Return the result-String

J, 11 bytes

Anonymous tacit prefix function.

|:@(,|.)^:2

Try it online!

|: transpose

@(…) the result of:

 , the argument followed by

 |. its reverse

^:2 and all this done twice

SNOBOL4 (CSNOBOL4), 119 113 bytes

	T =TABLE()
I	X =X + 1
	I =INPUT	:F(D)
	OUTPUT =T<X> =I REVERSE(I)	:(I)
D	X =X - 1
	OUTPUT =GT(X) T<X>	:S(D)
END	

Try it online!

Takes input as strings on STDIN, without spaces. This only works because the digits are 1-9 and would fail otherwise.

C (gcc), 114 111 bytes

• Saved three bytes thanks to Kevin Cruijssen; inverting the loops.

j,i;f(A,w,h)int*A;{for(i=h+h;i-->0;puts(""))for(j=w+w;j-->0;)printf("%d,",A[(i<h?i:h+h+~i)*w+(j<w?j:w+w+~j)]);}

Try it online!

C (gcc), 109 bytes (abusing ease of parsing)

• Thanks to Kevin Cruijssen for suggesting to only allow one-digit input integers; saved two bytes.

j,i;f(A,w,h)int*A;{for(i=h+h;i-->0;puts(""))for(j=w+w;j-->0;)putchar(A[(i<h?i:h+h+~i)*w+(j<w?j:w+w+~j)]+48);}

Try it online!

Charcoal, 5 bytes

θ‖Ｃ→↓

Try it online!

Thanks to ASCII-only for a better input format.

Add++, 30 bytes

D,f,@,bU€{r}B]{r}
D,r,@,dbR+

Try it online!

The footer simply transforms the nested array into the format in the question. Defines a function f, which expects a matrix (nested array) as an argument.

Julia 0.6, 55 49 bytes

~i=i:-1:1
!x=[x x[:,~end];x[~end,:] x[~end,~end]]

Try it online!

~(i) is a function to create slice from i down to 1.
So ~end gives the slice end:-1:1

!(x) is the function to do the rebuilding of the array.

V, 12 bytes

yGæGPÎy$æ_|P

Try it online!

Explanation:

yG              " Yank every line
  æG            " Reverse the order of the lines
    P           " Paste what we yanked
     Î          " On every line:
      y$        "   Yank the whole line
        æ_      "   Reverse the whole line
          |     "   Move to the beginning of the line
           P    "   Paste what we yanked