Generate binary matrices which are distinct up to reflections

Question

Here are all the 2x2 binary matrices

#0  #1  #2  #3  #4  #5  #6  #7  #8  #9  #10 #11 #12 #13 #14 #15
--  --  --  --  --  --  --  --  --  --  --  --  --  --  --  --  
00  00  00  00  01  01  01  01  10  10  10  10  11  11  11  11  
00  01  10  11  00  01  10  11  00  01  10  11  00  01  10  11  

Two binary square matrices are equivalent under the relation ~ if one can be mapped onto the other by any number of reflections in the horizontal or vertical axes.

#1 ~ #2 under reflection in the vertical axis so we only need to keep one of these (it doesn't matter which). Likewise #3 ~ #12, #6 ~ #9 and so on.

THE GOAL is to produce a program which takes a single input N and prints as many N x N binary matrices as exist such that all matrices in the output are distinct under the above relation.

In hand-wavey pseudocode, an admissible solution would be

define M[i] = N by N matrix with bit pattern equal to i

for i = 0 to (2^(N^2)) - 1
    valid = true
    for j = i+1 to (2^(N^2)) - 1
        if (equivalent(M[i], M[j]))
            valid = false
            break
    if (valid)
        print (M[i])

For the input N=2 one valid output would be

00  00  00  01  10  01  11
00  01  11  01  01  11  11

But by selecting different matrices from the same equivalence class another valid output would be

00  10  11  11  11  10  01
00  00  00  10  11  10  10

The order of matrices doesn't matter, the particular choice from equivalent matrices doesn't matter, and whitespace doesn't matter, output the matrices however you like as long as it's human-readable.

The output must be exhaustive.

Shortest code wins.

EDIT: this is my first golf post and I've changed my mind on the winning criteria.

Shortest code in a language not specifically designed for conciseness/golfing wins.

I hope it's not bad etiquette to change this criterion post-hoc, but I think doing it in a "normal" language is a much more interesting proposition.

Answer 1

J, 66 56 53 bytes

[:~.,~{.@/:~@(2:_&(][:,(;|.;|."1)&>)<)@$"#.2#:@i.@^*:

Brute-force search.

Usage

   f =: [:~.,~{.@/:~@(2:_&(][:,(;|.;|."1)&>)<)@$"#.2#:@i.@^*:
   f 2
┌───┬───┬───┬───┬───┬───┬───┐
│0 0│0 0│0 0│0 1│0 1│0 1│1 1│
│0 0│0 1│1 1│0 1│1 0│1 1│1 1│
└───┴───┴───┴───┴───┴───┴───┘
   # f 3
168
   # f 4
16576

Explanation

[:~.,~{.@/:~@(2:_&(][:,(;|.;|."1)&>)<)@$"#.2#:@i.@^*:  Input: integer n
                                                   *:  Square n
                                           2      ^    Compute m = 2 ^ (n ^ 2)
                                               i.@     Make a range [0, m)
                                            #:@        Convert each to binary digits
    ,~                                                    Pair, make [n, n]
                                       $"#.            Reshape each binary list
                                                          to a matrix with size [n, n]
             (                       )@                Operate on each
                                    <                    Box it, call x
              2:                                         The constant 2
                _&(                )                     Repeat that many times on x
                       (        )&>                        For each box
                            |."1                             Reverse by column
                         |.                                  Reverse by row
                           ;                                 Join them
                        ;                                    Join with initial
                    [:,                                    Flatten
                   ]                                       Return that as the new x
         /:~@                                          Sort each
      {.@                                              Take the head of each
[:~.                                                   Unique and return

Answer 2

Jelly, 19 bytes

Ṛ€;U;
2ḶṗṗµWdz¡Ṃµ€Q

Try it online!

How it works

2ḶṗṗµWdz¡Ṃµ€Q  Main link. Argument: n (integer)

2Ḷ             Unlength 2; yield [0, 1].
  ṗ            Cartesian product; construct all vectors of {0, 1}^n.
   ṗ           Cartesian product; construct all vectors of ({0, 1}^n)^n.
               This yields A, the array of all binary n×n matrices.
    µ     µ€   Begin a new, monadic chain and apply it to all matrices M in A.
     W           Wrap; yield [M].
      dz¡        Call the helper link n times, initially with argument [M], then
                 on the previous return value.
         Ṃ       Take the minimum of the results.
               This replaces all matrices with the lexicographical minimum of their
               equivalence classes, mapping equivalent matrices to the same matrix.
            Q  Unique; deduplicate the resulting array of matrices.

Ṛ€;U;          Helper link. Argument: L (array of matrices)

Ṛ€             Reverse the order of the rows of each M in L.
   U           Reverse the order of the columns of each M in L.
  ;            Concatenate the resulting matrix arrays.
    ;          Concatenate the result with L.

Answer 3

Pyth - 24 23 21 bytes

Wanna look for better way of getting all the reflections.

Thanks to @Pietu1998 for golfing me 2 bytes!

hM.gS+K_Bk_MMKcRQ^`T*

Try it online here.

Going to wait for golfing before doing a full explanation, but it essentially makes all possible binary matrices, then .groups them by the sorted list of all the possible reflections, then only takes one from each group.

Answer 4

JavaScript (ES6), 195 bytes

n=>[...Array(p=1<<n*n)].map(_=>(p++).toString(2).slice(1)).filter((s,i,a)=>![1,0,1].some(c=>a.indexOf((c?b.reverse():b=b.map(s=>[...s].reverse().join``)).join``)<i,b=s.match(eval(`/.{${n}}/g`))))

Returns strings representing all matrix entries concatenated e.g. 111101111 represents a 3×3 matrix of 1s with a 0 in the middle. Explanation:

n=>[...Array(p=1<<n*n)].map(            Enumerate all binary matrices
 _=>(p++).toString(2).slice(1)          Convert to padded binary
).filter((s,i,a)=>![1,0,1].some(        Check reflections of each matrix
 c=>a.indexOf((c?b.reverse():           Reverse the order of lines
  b=b.map(s=>[...s].reverse().join``    Or reverse each line
  )).join``)<i,                         Has this been seen before?
 b=s.match(eval(`/.{${n}}/g`))))        Reshape string into a square

Answer 5

Haskell, 100 bytes

import Data.List
r=reverse
e#n=mapM id$e<$[1..n]
f n=nubBy(\a b->elem a[r b,r<$>b,r$r<$>b])$"01"#n#n

Usage example: f 2 -> [["00","00"],["00","01"],["00","11"],["01","01"],["01","10"],["01","11"],["11","11"]].

How it works:

e#n=mapM id$e<$[1..n]        -- helper function: creates a list of all combinations
                             -- of the elements of e of length n
                             -- "01" # 2 -> ["00","01","10","11"]

                   "01"#n#n  -- creates all binary n x n matrices
nubBy                        -- remove duplicates according to the equivalence
                             -- relation
   \a b ->                   -- a equals b if
       a elem                -- a is an element of
         [r b,r<$>b,r$r<$>b] -- the list of reflections of b 

Answer 6

Mathematica, 94 bytes

DeleteDuplicatesBy[{0,1}~Tuples~{#,#},Sort@Join[Join@@Outer[Reverse,{#},{1,2,{1,2}},1],{#}]&]&

Answer 7

JavaScript (ES6), 184

This turned out to be quite similar to Neil's, but all in all the bag of tricks in javascript is not so diverse.

n=>eval("r=x=>[...x].reverse();for(l='',i=m=1<<n*n;i<m+m;i++)a=i.toString(2).slice(1).match(eval(`/.{${n}}/g`)),[b=a.map(x=>r(x).join``),r(a),r(b)].some(x=>~l.search(x))?0:l+=a+`\n`")

Less golfed

n=>{
  r = x =>[...x].reverse();
  for(l = '', i = m = 1<<n*n; i < m+m; i++)
    a = i.toString(2).slice(1).match(eval(`/.{${n}}/g`)), // base matrix as an array of strings
    b = a.map(x => r(x).join``), // horizontal reflection
    c = r(a), // vertical reflection
    d = r(b), // both reflections
    // check if already found 
    [b, c, d].some(x => ~l.search(x)) // using search, arrays are converted to comma separated strings 
      ? 0 
      : l += a+`\n` // add new found to list (again as a comma separated string)
  return l
}

Test Beware, even for input 4 the running time is overly long

f=n=>eval("r=x=>[...x].reverse();for(l='',i=m=1<<n*n;i<m+m;i++)a=i.toString(2).slice(1).match(eval(`/.{${n}}/g`)),[b=a.map(x=>r(x).join``),r(a),r(b)].some(x=>~l.search(x))?0:l+=a+`\n`")

function update() {
  var i=+I.value;
  
  result = f(i)
  count = result.split('\n').length
  O.textContent = count+'\n'+result
}

update()

Input <select id=I onchange="update()"><option>2<option>3<option>4<option>5</select>
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