Create a checkerboard matrix

Question 1

Take a positive integern as input, and output an-by-n checkerboard matrix consisting of1 and0.

The top left digit should always be1.

Test cases:

n = 11n = 21 00 1n = 31 0 10 1 01 0 1n = 41 0 1 00 1 0 11 0 1 00 1 0 1

Input and output formats are optional. Outputting the matrix as a list of lists is accepted.

Question 2

Is a list of strings OK?

Question 3

Yes, that's OK.

Question 4

Related.

Question 5

Your examples show spaces between numbers on the same row, is that required, so as to look more like a square?

Question 6

@BradC it's not required. The first approachhere is valid.

Question 7

Jelly, 4 bytes

52 seconds!

+€ḶḂ

Try it online!

Question 8

"52 seconds!" like I'm not used to it...

Question 9

Do ya'll have, like, a beeper, you wear 24/7 for new PPCG challenges?

Question 10

@carusocomputing Those who have a faster internet connection are usually the lucky ones that will win.

Question 11

MATL, 5 bytes

:otYT

Try it atMATL online!

Explanation

Consider input4 as an example.

:    % Implicit input, n. Push range [1 2 ... n]     %   STACK: [1 2 3 4]o    % Parity, element-wise     %   STACK: [1 0 1 0]t    % Duplicate     %   STACK: [1 0 1 0], [1 0 1 0]YT   % Toeplitz matrix with two inputs. Implicit display     %   STACK: [1 0 1 0;     %           0 1 0 1;     %           1 0 1 0;     5           0 1 0 1]

Question 12

Haskell,504139 38 bytes

Thanks to nimi and xnor for helping to shave off a total of9 10 bytes

f n=r[r"10",r"01"]where r=take n.cycle

Alternately, for one byte more:

(!)=(.cycle).takef n=n![n!"10",n!"01"]

or:

r=flip take.cyclef n=r[r"10"n,r"01"n]n

Probably suboptimal, but a clean, straightforward approach.

Question 13

concat.repeat iscycle:n!l=take n$cycle l. If you go pointfree it saves one more byte:(!)=(.cycle).take.

Question 14

Lovely! I knew there was a builtin for that, but couldn't remember the name for the life of me

Question 15

I was going to suggestf n|r<-take n.cycle=r[r"10",r"01"] or similar. but Haskell seems to infer the wrong type forr? It works with explicit typingf n|r<-take n.cycle::[a]->[a]=r[r"10",r"01"].

Question 16

@JulianWolf Haskell seems to havetrouble inferring polymorphic types

Question 17

@zbw I thought this was the case but usingNoMonomorphismRestriction didn't help. Nor didRank2Types orRankNTypes. Do you know what's going on there?

Question 18

Japt, 6 bytes

ÆÇ+X v

Test it online! (Uses-Q flag for easier visualisation)

Explanation

 Æ   Ç   +X vUoX{UoZ{Z+X v}}  // Ungolfed                 // Implicit: U = input numberUoX{          }  // Create the range [0...U), and map each item X to    UoZ{     }   //   create the range [0...U), and map each item Z to        Z+X      //     Z + X            v    //     is divisible by 2.                 // Implicit: output result of last expression

An interesting thing to note is thatv isnot a "divisible by 2" built-in. Instead, it's a "divisible by X" built-in. However, unlike most golfing languages, Japt's functions do not have fixed arity (they can accept any number of right-arguments). When given 0 right-arguments,v assumes you wanted2, and so acts exactly like it was given2 instead of nothing.

Question 19

V,16, 15 bytes

Ài10ÀñÙxñÎÀlD

Try it online!

Hexdump:

00000000: c069 3130 1bc0 adf1 d978 f1ce c06c 44    .i10.....x...lD

Question 20

APL (Dyalog), 8 bytes

~2|⍳∘.+⍳

Try it online!

Explanation

Let's call the argumentn.

⍳∘.+⍳

This creates a matrix

1+1 1+2 1+2 .. 1+n2+1 2+2 2+3 .. 2+n...n+1 n+2 n+3 .. n+n

Then2| takes modulo 2 of the matrix (it vectorises) after which~ takes the NOT of the result.

Question 21

JavaScript ES6,555451 46 bytes

Saved 1 byte thanks to @Neil

Saved 2 bytes thanks to @Arnauld

n=>[...Array(n)].map((_,i,a)=>a.map(_=>++i&1))

Try it online!

This outputs as an array of arrays. JavaScript ranges are pretty unweildy but I use[...Array(n)] which generates an array of sizen

Question 22

It's still a byte shorter to use the index parameters:n=>[...Array(n)].map((_,i,a)=>a.map((_,j)=>(i+j+1)%2))

Question 23

@Neil huh, I never thought to use the third parameter in map, thanks!

Question 24

@Arnauld thanks! that inspired me to save 5 more bytes!

Question 25

J, 9 bytes

<0&=$&1 0

Try it online!

Question 26

05AB1E,9 7 bytes

-2 bytes thanks to Emigna

LDÈD_‚è

Try it online!

Explanation

LDÈD_‚sè» Argument nLD        Push list [1 .. n], duplicate  ÈD      Map is_uneven, duplicate    _     Negate boolean (0 -> 1, 1 -> 0)     ‚    List of top two elements of stack      è   For each i in [1 .. n], get element at i in above created list          In 05AB1E the element at index 2 in [0, 1] is 0 again

Question 27

You can cut the» as list-of-lists output is okay and you can also removes.

Question 28

Explanation is a bit irrelevant.

Question 29

Bash + rs, 39

3 bytes saved thanks to @roblogic

eval echo \$[~{1..$1}+{1..$1}\&1]|rs $1

Try it online!

Question 30

you can do simplyrs $1, saving 3 bytes

Question 31

Mathematica, 25 bytes

1-Plus~Array~{#,#}~Mod~2&

Question 32

Clojure, 36 bytes

#(take %(partition % 1(cycle[1 0])))

Yay, right tool for the job.

Question 33

Retina,33 30 bytes

.+$*1$_¶1110T`10`01`¶.+¶

Try it online! Explanation: The first stage converts the input to unary using1s (conveniently!) while the second stage turns the value into a square. The third stage inverts alternate bits on each row while the last stage inverts bits on alternate rows. Edit: Saved 3 bytes thanks to @MartinEnder.

Question 34

$`1$' is just$_.

Question 35

01 is justd. (Post is too old for me to bother editing it.)

Question 36

Java (OpenJDK 8),80 77 bytes

-3 bytes thanks to Kevin Cruijssen

j->{String s="1";for(int i=1;i<j*j;s+=i++/j+i%j&1)s+=1>i%j?"\n":"";return s;}

Try it online!

Oh look, a semi-reasonable length java answer, with lots of fun operators.

lambda which takes an int and returns a String. Works by using the row number and column number using / and % to determine which value it should be, mod 2;

Ungolfed:

j->{    String s="1";    for(int i=1; i<j*j; s+= i++/j + i%j&1 )        s+= 1>i%j ? "\n" : "";    return s;}

Question 37

You can remove the space to save a byte. The challenge states the output format is flexible. Oh, and you can save two more bytes by changing(i++/j+i%j)%2 toi++/j+i%j&1 so you won't need those parenthesis. Which make the total 1 byte shorter than my nested for-loop solution (n->{String r="";for(int i=0,j;i++<n;r+="\n")for(j=0;j<n;r+=j+++i&1);return r;}), so +1 from me. :)

Question 38

@KevinCruijssen Yeah I was still waiting on a response on the space. I didn't think about & having higher precedence than % and &1 == %2

Question 39

Arturo,3936 32 bytes

$[n][map n'x->map n'y->%x+y+1 2]

Try it

-3 thanks to alephalpha's simpler method

Prettified and rearranged for clarity:

$[n][                     ; a function taking an argument n    map n 'x ->           ; map over 1..n, assign current elt to x        map n 'y ->       ; map over 1..n again, assign current elt to y            (x+y+1)%2     ; what it looks like]                         ; end function

Question 40

MATL, 7 bytes

:t!+2\~

Try it online!

Explanation:

         % Implicit input (n):        % Range from 1-n, [1,2,3] t       % Duplicate, [1,2,3], [1,2,3]  !      % Transpose, [1,2,3], [1;2;3]   +     % Add        [2,3,4; 3,4,5; 4,5,6]    2    % Push 2     [2,3,4; 3,4,5; 4,5,6], 2     \   % Modulus    [0,1,0; 1,0,1; 0,1,0]      ~  % Negate     [1,0,1; 0,1,0; 1,0,1]

_{Note: I started solving this in MATLafter I posted the challenge.}

Question 41

Equivalent, and shorter::&+o~

Question 42

Still learning :-) I'll update tomorrow. I liked your other approach too :-)

Question 43

This is what I came up with, too. And hey, you only use thepure MATL instruction set, not those peskyY-modified instructions @LuisMendo uses.

Question 44

@Sanchises Pesky,huh? :-P

Question 45

Brachylog, 19 bytes

⟦₁Rg;Rz{z{++₁%₂}ᵐ}ᵐ

Try it online!

Question 46

Charcoal, 8 bytes

ＵＯＮ10¶01

Try it online! Explanation: This roughly translates to the following verbose code (unfortunately the deverbosifier is currently appending an unnecessary separator):

Oblong(InputNumber(), "10\n01");

Question 47

Brachylog, 15 bytes

^₂⟦₁%₂ᵐ;?ḍ₎pᵐ.\

Try it online!

Explanation

Example Input: 4^₂               Square:                            16  ⟦₁             1-indexed Range:                   [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16]    %₂ᵐ          Map Mod 2:                         [1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0]       ;?ḍ₎      Input-Chotomize:                   [[1,0,1,0],[0,1,0,1],[1,0,1,0],[0,1,0,1]]           pᵐ.   Map permute such that..             .\  ..the output is its own transpose: [[1,0,1,0],[0,1,0,1],[1,0,1,0],[0,1,0,1]]

Question 48

Pyth, 9 bytes

VQm%+hdN2

Try this!

another 9 byte solution:

mm%+hdk2Q

Try it!

Question 49

///, 87 bytes + input

/V/\\\///D/VV//*/k#D#k/k#D&k/k&DVk/k\D/SD/#/rDSkk/10DSk/1D&/V#rV#0r;VV0;VVV1;V\D/r/S/&[unary input in asterisks]

Try it online! (input for 4)

Unary input in`1`s, 95 bytes + input

/V/\\\///D/VV//&1/k#&D&|D/#k/k#D&k/k&DVk/k\D/SD/#/rDSkk/10DSk/1D&/V#rV#0r;VV0;VVV1;V\D/r/S/&&[unary input in ones]|

Try it online! (input for 8)

How does this work?

V andD are to golf\/ and// respectively.
/*/k#/ and/&1/k#&//&|// separate the input into the equivalent of'k#'*len(input())
/#k//k#//&k/k&//\/k/k\// move all theks to the/r/S/ block
Ss are just used to pad instances whereks come after/s so that they don't get moved elsewhere, and theSs are then removed
#s are then turned intor\ns
The string ofks is turned into an alternating1010... string
Ther\ns are turned into1010...\ns
Every pair of1010...\n1010\n is turned into1010...\01010...;\n
Either0; or1; are trimmed off (because the01010... string is too long by 1)

Question 50

Swi-Prolog, 142 bytes.

t(0,1).t(1,0).r([],_).r([H|T],H):-t(H,I),r(T,I).f([],_,_).f([H|T],N,B):-length(H,N),r(H,B),t(B,D),f(T,N,D).c(N,C):-length(C,N),f(C,N,1).

Try online -http://swish.swi-prolog.org/p/BuabBPrw.pl

It outputs a nested list, so the rules say:

t() is a toggle, it makes the 0 -> 1 and 1 -> 0.
r() succeeds for an individual row, which is a recursive check down a row that it is alternate ones and zeros only.
f() recursively checks all the rows, that they are the right length, that they are valid rows withr() and that each row starts with a differing 0/1.
c(N,C) says that C is a valid checkerboard of size N if the number of rows (nested lists) is N, and the helper f succeeds.

Test Cases:

Question 51

Can't you strip off all newlines?

Question 52

Nekomata, 5 bytes

ᵒ+→2%

Attempt This Online!

ᵒ+→2%ᵒ+       Create an (input x input) matrix where the element at (i,j) is i+j  →      Increment   2%    Mod 2

Question 53

AWK, 57 bytes

{for(;i++<$1^2;$1%2||i%$1||x=!x)printf(x=!x)(i%$1?FS:RS)}

Attempt This Online!

Question 54

QBIC, 19 bytes

[:|?[b|?(a+c+1)%2';

Explanation

[:|         FOR a = 1 to b (b is read from cmd line)?           PRINT - linsert a linebreak in the output[b|         FOR c = 1 to b?(a+c+1)%2  PRINT a=c=1 modulo 2 (giving us the 1's and 0's';            PRINT is followed b a literal semi-colon, suppressing newlines and               tabs. Printing numbers in QBasic adds one space automatically.

Question 55

PHP, 56 bytes

Output as string

for(;$i<$argn**2;)echo++$i%2^$n&1,$i%$argn?"":"".!++$n;

Try it online!

PHP, 66 bytes

Output as 2 D array

for(;$i<$argn**2;$i%$argn?:++$n)$r[+$n][]=++$i%2^$n&1;print_r($r);

Try it online!

Question 56

CJam, 17 bytes

{_[__AAb*<_:!]*<}

Try it online!

Returns a list (TIO link has formatted output).

Question 57

out-golfed

Question 58

@Challenger5 Sorry you can't outgolf with deleted answer.

Question 59

Mathematica, 23 bytes

ToeplitzMatrix@#~Mod~2&

Question 60

Octave, 24 bytes

@(n)~mod((a=(1:n))+a',2)

Try it online!

Or the same length:

@(n)mod(toeplitz(1:n),2)

Try it online!

Question 61

Mathematica, 28 bytes

Cos[+##/2Pi]^2&~Array~{#,#}&

Pure function taking a positive integer as input and returning a 2D array. Uses the periodic function cos²(πx/2) to generate the 1s and 0s.

For a little more fun, how about the 32-byte solution

Sign@Zeta[1-+##]^2&~Array~{#,#}&

which uses the locations of the trivial zeros of the Riemann zeta function.

Leaky Nun 50.6k6 gold badges115 silver badges291 bronze badges · Accepted Answer · 2017-06-15 17:33:08Z

13

\$\begingroup\$

Jelly, 4 bytes

52 seconds!

+€ḶḂ

Try it online!

Share

Improve this answer

answeredJun 15, 2017 at 17:33

Leaky Nun

50.6k6 gold badges115 silver badges291 bronze badges

\$\endgroup\$

3

8
\$\begingroup\$"52 seconds!" like I'm not used to it...\$\endgroup\$
Erik the Outgolfer
– Erik the Outgolfer
2017-06-15 17:35:43 +00:00
CommentedJun 15, 2017 at 17:35
8
\$\begingroup\$Do ya'll have, like, a beeper, you wear 24/7 for new PPCG challenges?\$\endgroup\$
Magic Octopus Urn
– Magic Octopus Urn
2017-06-16 20:43:24 +00:00
CommentedJun 16, 2017 at 20:43
\$\begingroup\$@carusocomputing Those who have a faster internet connection are usually the lucky ones that will win.\$\endgroup\$
Erik the Outgolfer
– Erik the Outgolfer
2017-06-17 14:16:00 +00:00
CommentedJun 17, 2017 at 14:16

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Movatterモバイル変換

Create a checkerboard matrix

64 Answers64

Jelly, 4 bytes

MATL, 5 bytes

Explanation

Haskell,504139 38 bytes

Japt, 6 bytes

Explanation

V,16, 15 bytes

APL (Dyalog), 8 bytes

Explanation

JavaScript ES6,555451 46 bytes

J, 9 bytes

05AB1E,9 7 bytes

Explanation

Bash + rs, 39

Mathematica, 25 bytes

Clojure, 36 bytes

Retina,33 30 bytes

Java (OpenJDK 8),80 77 bytes

Arturo,3936 32 bytes

MATL, 7 bytes

Brachylog, 19 bytes

Charcoal, 8 bytes

Brachylog, 15 bytes

Explanation

Pyth, 9 bytes

///, 87 bytes + input

Unary input in1s, 95 bytes + input

How does this work?

Swi-Prolog, 142 bytes.

Nekomata, 5 bytes

AWK, 57 bytes

QBIC, 19 bytes

Explanation

PHP, 56 bytes

PHP, 66 bytes

CJam, 17 bytes

Mathematica, 23 bytes

Octave, 24 bytes

Mathematica, 28 bytes

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