# Create a percent sign

Given an integer n ≥ 1, output a 2D representation of a percent sign of width n. The construction goes as follows:

1. Create an n by n matrix (or list of lists) filled with zeroes.
2. Insert ones in the top-left and bottom-right corners.
3. Place ones on the diagonal from the bottom-left to the top-right.

For input n = 4, this construction would look like:

1. 4x4 matrix of 0s
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
2. 1s in TL and BR corners
1 0 0 0
0 0 0 0
0 0 0 0
0 0 0 1
3. 1s across BL-TR diagonal
1 0 0 1
0 0 1 0
0 1 0 0
1 0 0 1


This is a , so the shortest program in bytes wins.

I use a matrix of 1s and 0s, but it is also acceptable to use a string of any non-whitespace character and spaces. So, the example above could look like:

#  #
#
#
#  #


or

#     #
#
#
#     #


## Test cases

n
output

1
1

2
1 1
1 1

3
1 0 1
0 1 0
1 0 1

4
1 0 0 1
0 0 1 0
0 1 0 0
1 0 0 1

10
1 0 0 0 0 0 0 0 0 1
0 0 0 0 0 0 0 0 1 0
0 0 0 0 0 0 0 1 0 0
0 0 0 0 0 0 1 0 0 0
0 0 0 0 0 1 0 0 0 0
0 0 0 0 1 0 0 0 0 0
0 0 0 1 0 0 0 0 0 0
0 0 1 0 0 0 0 0 0 0
0 1 0 0 0 0 0 0 0 0
1 0 0 0 0 0 0 0 0 1


## Final note

Adding an explanation would be greatly appreciated.

• Can our solutions be 0-indexed? – Kritixi Lithos Jul 21 '17 at 17:41
• @Cowsquack I'd say no. You're receiving the width, not an index. – Conor O'Brien Jul 21 '17 at 17:44
• Can we output a list of lists? – xnor Jul 21 '17 at 18:02
• @xnor Yes; list of lists and matrix are synonymous in my post. I'll add that to the question – Conor O'Brien Jul 21 '17 at 18:15
• Note that this is '1'+'0'*(n-2) with whitespace inserted – CalculatorFeline Jul 21 '17 at 21:30

# Jelly, 6 bytes

²Rm’Ṭs


Try it online!

### How it works

²Rm’Ṭs  Main link. Argument: n

²       Square; yield n².
R      Range; yield [1, ..., n²].
’    Decrement; yield n-1.
m     Modular; yield every (n-1)-th element of the range, staring with the first.
Ṭ   Untruth; yield a Boolean array with 1's at the specified indices.
s  Split the resulting array into chunks of length n, creating a matrix.

• Also, ²Ḷ%’¬s or +þ%’=2 – ETHproductions Jul 21 '17 at 17:52
• ²Ḷọ’s is so close... – Dennis Jul 21 '17 at 17:57
• If only there were a 1-byte "x is divisible by y" link... – ETHproductions Jul 21 '17 at 17:58
• @ETHproductions There's ḍ@ but that's two bytes. – Erik the Outgolfer Jul 21 '17 at 19:14
• And I thought I was clever with ⁼þµ+1¦Ṫṁ³UG...until a Dennis ²-something solution popped up. – Erik the Outgolfer Jul 21 '17 at 19:15

## JavaScript (ES6), 52 bytes

n=>[...Array(n)].map((_,y,a)=>a.map(_=>y++%~-n<1|0))


# V, 15 bytes

Àé ÀÄ|r#L.|ò.kl


Try it online!

### Explanation

Àé<space>        " Argument times insert a space
ÀÄ               " Argument times duplicate this line
" This gives an arg-by-arg matrix of spaces
"  and brings the cursor to the end of the first line
|r#              " Go to the beginning of this line and replace the first character with #
L.               " Go to the end of this matrix (bottom-right corner) and replace that character with a #
|                " Go to the beginning of the last line
ò                " Recursively do:
.               "  Repeat the last action, r#, replace the character under the cursor with #
kl              "  Go 1 up and 1 right


# Python 2, 58 57 bytes

n=input()
x='#'.ljust(n-1)*3
exec'print x[:n];x=x[1:];'*n


Try it online!

# GNU APL, 17 15 bytes

{1=⍵∨⍵⍵⍴1=⍳⍵-1}


This is one weird day ... GNU actually beat Dyalog APL ... woah.

TIO doesn't support GNU APL ...

Explanation (input is ⍵):

1=⍳⍵-1 - 1 followed by ⍵-2 0's
⍵⍵⍴    - fit into a square
⍵∨     - gcd ⍵ (0 gcd n = n)
1=     - test each element for equality with 1

• Ninja'd? – Kritixi Lithos Jul 21 '17 at 18:25
• There ... take that. – Zacharý Jul 21 '17 at 18:28
• Can't believe I actually had to break out my old GNU APL, wow. – Zacharý Jul 21 '17 at 18:30
• And take that!! – Zacharý Jul 21 '17 at 18:36
• Ooh, I am going to take inspiration from the 1=⍵∨ and implement it in my solution – Kritixi Lithos Jul 21 '17 at 18:44

# Python 2, 46 bytes

lambda n:zip(*[iter(10L**n[:-3]*-~n+'1')]*n)


Try it online!

Outputs like

[('1', '0', '0', '1'), ('0', '0', '1', '0'), ('0', '1', '0', '0'), ('1', '0', '0', '1')]


# Python 2, 48 bytes

lambda n:zip(*[iter([1]+(n*[0]+[1])[2:]*-~n)]*n)


Try it online!

Outputs like

[(1, 0, 0, 1), (0, 0, 1, 0), (0, 1, 0, 0), (1, 0, 0, 1)]


# Python 3, 48 bytes

lambda n:('%d'*n+'\n')*n%(1,*(*[0]*n,1)[2:]*-~n)


Try it online!

A quite different string-substitution approach in Python 3. Outputs like:

1001
0010
0100
1001

• Can't you make 10L 10? – Zacharý Jul 30 '17 at 20:08
• @Zacharý I'm relying on there always being an L at the end so I can cut the same number of characters off the end of large numbers and small ones. – xnor Jul 30 '17 at 20:20
• Oh, sorry, I mistakenly thought you were only using it as the number. I never knew 10 and 10L were different. – Zacharý Jul 30 '17 at 20:22

# Jelly, 9 bytes

=þ¹UF1Q¦s


Try it online!

### How it works

=þ¹UF1Q¦s  Main link. Argument: n

¹        Identity; yield n.
=þ         Equals table; compare each i in [1, ..., n] with each j in [1, ..., n].
This yields the n×n identity matrix.
U       Upend; reverse each row.
F      Flatten the matrix.
¦   Sparse application:
Q        Unique; yield the unique elements of the constructed array, i.e.,
[1] if n = 1 and [0, 1] if n > 1.
1         Yield 1.
This replaces the elements at indices 0 (last) and 1 (first) with 1.
s  Split the resulting array into chunks of length n.


# APL (Dyalog), 18 bytes

{⍵=1:⍵⋄⍵ ⍵⍴1=⍳⍵-1}


Try it online!

Making this work for input 1 has added 6 bytes.

Looking at testcase 4, we see the output is

1 0 0 1
0 0 1 0
0 1 0 0
1 0 0 1


This is basically 1 0 0 repeated throughout the matrix. In other words, 1 0 0 shaped in a 4-by-4 matrix. So in this solution, we first generate this vector with 1 and trailing 0s using 1=⍳⍵-1 and then shape it using ⍵ ⍵⍴. But this borks for input 1, so we need to create a conditional and gain 6 bytes...

{⍵=1:⍵⋄⍵ ⍵⍴1=⍳⍵-1}    The right argument is ⍵
⍵=1:⍵                 If ⍵ is 1 return itself
⋄                      Otherwise
⍳⍵-1                   Create a range 1 .. ⍵-1
1=                     Equals 1; 1 0 0 {⍵-2 0's} ...
⍵ ⍵⍴                   Shape in a ⍵-by-⍵ matrix


At first my approach was to recursively generate the transposed identity matrix, but then fixing the first and last line required some ugly/lengthy case distinctions. So I looked for another way to generate the identity matrix which is how I found this idea.

f n=[[sum[1|x+yelem[2,n+1,2*n]]|y<-[1..n]]|x<-[1..n]]


Try it online!

### Explanation

[[x+y|y<-[1..n]]|x<-[1..n]]


generates this matrix (for n=4):

[2,3,4,5]
[3,4,5,6]
[4,5,6,7]
[5,6,7,8]


As you can see the top left element is 2 (in general), all the diagonal elements are 5 (in general n+1) and the bottom right element is 8 (in general 2*n). So all we need to do is to check if x+y is an element of [2,n+1,2*n].

# R, 54 42 bytes

-12 bytes thanks to Jarko Dubbeldam

n=scan();m=diag(n)[,n:1];m[1,1]=m[n,n]=1;m


returns a matrix; reads from stdin. creates an identity matrix diag(n), flips it top to bottom [,n:1], sets the top left and bottom right to 1, and then writes to console ('') with width n.

Try it online!

• You are allowed to output a matrix, so you can save a few bytes by turning it into a function (pryr::f). – JAD Jul 21 '17 at 19:03
• @JarkoDubbeldam I could, but then I think I'd have to change the language to R+pryr so I'd consider that a separate language; you're free to submit that! Then you could use the idea from Cows quack's answer which I think would be even shorter than this in that context (a 1-liner). – Giuseppe Jul 21 '17 at 20:04
• Hmm, I am unsure where to draw the line to be honest. Would you consider any library used a different language? – JAD Jul 21 '17 at 20:25
• Also, using function(n) would probably still be shorter – JAD Jul 21 '17 at 20:30
• Which is shorter than the oneliner implementation you referenced: function(n)matrix(rep(c(1,rep(0,n-2)),n+1),n,n) – JAD Jul 21 '17 at 20:35

# MATL, 7 bytes

XyPl5L(


Try it at MATL Online!

### Explanation

Create identity matrix (Xy), flip vertically (P), write (() value 1 (l) to the first and last entries (5L), which are the top left and bottom right.

# Dyalog APL, 1211 10 bytes

,⍨⍴×,2↓⊢↑×


Try it online

-1 byte thanks to lstefano.

## How?

,⍨⍴×,2↓⊢↑×
⊢↑× - argument-length extension of the sign of the argument (1)
2↓    - Drop the first two elements
×,      - Prepend a one
,⍨⍴        - Shape into a square array with dimensions of input x input

• I seriously don't think this can be golfed anymore... wow. – Zacharý Jul 23 '17 at 15:35
• It can: ,⍨⍴×,2↓⊢↑× (10 bytes). I am tempted to add: don't use too many commutes... :-P – lstefano Aug 2 '17 at 8:49
• – lstefano Aug 2 '17 at 8:53
• You've got to be kidding me, wow. Nice abuse of signum. – Zacharý Aug 14 '17 at 18:09

# C# (.NET Core),121 91 88 bytes

-30 bytes because the old way was stupid.

-3 bytes by moving around the variable initialization

n=>{int i=0,k=n-1;int[,]b=new int[n,n];b[0,0]=b[k,k]=1;for(;i<n;)b[i++,k--]=1;return b;}


Try it online!

Loops iterates down the array to fill in the 1's. Returns an array of 1's and 0's.

• Declare b as var to save some bytes. – TheLethalCoder Jul 24 '17 at 8:02

# 05AB1E, 1411 7 bytes

n<ÝI<Öô


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Explanation

n<Ý      # push range [0 ... n^2-1]
I<Ö   # check each for equality to 0 when modulus with n-1 is taken
ô  # split in pieces of size n


# Charcoal, 1412 7 bytes

-5 bytes thanks to Neil!

↗Ｎ⸿/‖Ｏ↘


Try it online!

• I don't think this can be any shorter... – Erik the Outgolfer Jul 21 '17 at 19:25
• Well, first I trimmed it to Ｎν◨/ν←↙ν‖Ｏ↘, but then I came up with ↗Ｎ⸿/‖Ｏ↘! – Neil Jul 21 '17 at 19:27
• @Neil Wow, I don't even know what ⸿ does. Does it reset to original position? – notjagan Jul 21 '17 at 19:41
• No, ⸿ is like ¶ in that it moves down a row but it always goes to column zero (as measured by Ｊ) rather than the column at the beginning of the string, so for example Ｊ⁵¦⁵⸿ is the same as Ｊ⁰¦⁶. – Neil Jul 21 '17 at 23:05

## C++, 144 bytes

#include<string>
#define S std::string
S p(int n){S r;for(int i=0;i<n;++i){r+=S(n,32);r[r.size()-1-i]=35;r+=10;}r[0]=r[r.size()-2]=35;return r;}


It takes advantage of the one byte difference between '#' and 35

• Where exactly does your code take advantage of the one byte difference between '#' and 35? – Zacharý Jul 30 '17 at 22:41
• @Zacharý It seems it was in my IDE x) – HatsuPointerKun Jul 30 '17 at 22:58

# Mathematica, 72 bytes

(s=Table[0,#,#];s[[1,1]]=s[[#,#]]=1;Table[s[[#+1-i,i]]=1,{i,#}];Grid@s)&


input

[5]

output

1 0 0 0 1
0 0 0 1 0
0 0 1 0 0
0 1 0 0 0
1 0 0 0 1

• The problem doesn't ask you to print/display it, so you can replace Grid@s with s to save 5 bytes. – Mark S. Jul 30 '17 at 22:56

# Python 2, 86 62 bytes

n=input();a=('1'+'0'*(n-2))*2+'1'
exec'print a[:n];a=a[1:];'*n


Try it online!

-24 bytes: Thanks to an idea from Rod!

# PowerShell, 67 bytes

param($n)0..--$n|%{-join(("1"+"0"*(($n-1),0)[!$n])*3)[$_..($_+$n)]}  Try it online! Takes input $n and loops from 0 to --$n (i.e., $n pre-decremented). Each iteration, we construct a string of 1 followed by $n-1 0s, then multiply that out 3 times (e.g., 100010001000 for input of 5). Then we index into that on a rotating basis starting from 0 to 0 +$n. Those characters are -joined into a string, which is left on the pipeline. Output is implicit.

(NB -- This requires an additional 9 bytes to handle the special case of n=1. Below is the 58-byte code if we're guaranteed n>1)

param($n)0..--$n|%{-join(("1"+"0"*($n-1))*3)[$_..($_+$n)]}


# Dyalog APL v16, 23 bytes

{(1@(1 1)(⍵ ⍵))⌽∘.=⍨⍳⍵}


Try it online!

Explanation:

{(1@(1 1)(⍵ ⍵))⌽∘.=⍨⍳⍵} -(input ⍵)
∘.=⍨⍳⍵  - identity matrix with size ⍵×⍵
⌽        - flip that
(1@(1 1)(⍵ ⍵))         - place 1 into the corners using the v16 operator @ (At)


## Lua, 117 bytes

m=arg[1]+0 for y=m,1,-1 do s=""for x=1,m do s=s..((x==1 and y==m or x==m and y==1 or x==y)and"#"or" ")end print(s)end

Try it

Code is pretty simple. It sets m to the first argument, then adds 0 to it to convert it to a number, then iterates backwards for the Y coord, forward through the X coord and will put a # if x==y or if it's the other corners.

This program never uses the keyword "if".

# Octave, 37 bytes

@(n)sparse([1 n:-1:1 n],[1 1:n n],!0)


Try it online!

Generates a sparse matrix representing the percent sign.

# Japt, 12 bytes

²ovUÉ hT1 òU


Returns a 2D array / matrix.

Try it online! using the -Q flag to show array-formatted output.

## Explanation

²ovUÉ hT1 òU


Implicit: U = input integer

²o


Square U (²), create the array [0, U*U) (o), and map each item by...

vUÉ


1 if it's divisible (v) by U-1 (UÉ), else 0.

hT1


Set the item (h) at index 0 (T) to 1.

òU


Split the array into slices (ò) of length U.

• I don't think you actually need the hT1, as 0 is technically already divisible by U for every U. Other than that, great job :-) – ETHproductions Jul 21 '17 at 19:49
• @ETHproductions That was added to deal with an input of 1. Without it, it returns [[0]] because apparently zero is not divisible by zero. – Justin Mariner Jul 21 '17 at 19:52
• Ah, dang it. I don't know if I should fix that though... – ETHproductions Jul 21 '17 at 19:57

# PHP, 53 bytes

for(;$i<$l*$l;)echo($i++%($l-1)?0:1).($i%$l?'':"\n");  The length of the side of the matrix is $l. This code has a PHP Notice and even a PHP Warning for division by 0 when $l=0, but does the job! • It seems that you expect the input to be stored in a predefined variable (->$l). Unfortunately this is not one of our accepted ways to take input. In the linked meta post you'll find alternatives, e.g. using command line arguments as seen in ricdesi's answer. – nimi Jul 22 '17 at 10:03
• completed and golfed: while($i**.5<$n=$argn)echo$i++%~-$n?0:1,"\n"[$i%$n]; or while($i**.5<$n=$argn)echo+!($i++%~-$n),"\n"[$i%$n]; (52 bytes each) – Titus Jul 22 '17 at 16:05
• Needs <? at the beginning. – manassehkatz-Reinstate Monica Jul 23 '17 at 4:17

# Python 2, 93 bytes

n=input()
a='1'+'0'*(n-2)+'1'
print a
for i in range(1,n-1):print str(10**i).zfill(n)
print a


Try it online!

• Good try, but doesnt work for n=1. – mu 無 Jul 22 '17 at 6:35

# Ruby, 47 bytes

->n{([1]+[0]*(n-2)).cycle.each_slice(n).take n}


It returns an array of arrays.

The code is pretty straightforward.

• It creates a n-1 array with 1 as the first element and the rest filled with 0s (e.g. [1, 0, 0, 0])
• It repeats it
• It takes n slices of n elements

Try it online!

# J, 14 bytes

-]\*:$1,0$~-&2


Ungolfed:

- ]\ (*: $(1,0$~ -&2))


Try it online!

• Food for thought: a 10 byte solution exists :) – Conor O'Brien Jul 29 '17 at 7:13
• @ConorO'Brien Damn you. It's already past 3 am here :P – Jonah Jul 29 '17 at 7:13
• Same here, and here we are :D – Conor O'Brien Jul 29 '17 at 7:14
• @ConorO'Brien Was it 0=<:|i.@,~? – miles Jul 30 '17 at 4:56
• @miles yes, it was :) – Conor O'Brien Jul 30 '17 at 4:58

# Python 3, 97 bytes

def f(n):
m=[[0+(j==n-i-1)for j in range(n)]for i in range(n)]
m[0][0]=1
m[-1]=m[0]
return m


# Explanation

m=[[0+(j==n-i-1)for j in range(n)]for i in range(n)]

This is a list comprehension, the 0+(j==n-i-1) is a shorter way to convert j==n-i-1 to an int (as opposed to int function) and then m[-1]=m[0] is shorter than making bottom right 1, as top and bottom rows are identical.

## Forth, 273 ( without comments ) 170 ( golfed-ish )

: % 2 base ! cr dup 1- 1 swap lshift 1 or . cr 2 over 2 - dup 0< 0= if
0 ?do 2dup s>d rot <# 0 ?do # loop #> type cr 2*  loop
1 or . else drop drop then cr drop decimal ;


## ( 273 version to clarify commented version: )

: newbase
base @ swap base ! ;
: 0u.r
swap s>d rot <# 0 ?do # loop #> type ;
: frame
1- 1 swap lshift 1 or ;
: %
2 newbase swap
cr dup frame . cr
2 over 2 -
dup 0< 0= if
0 ?do
2dup swap 0u.r cr
2*
loop
1 or .
else
drop drop
then
cr
drop base ! ;


( Note that, since whitespace is the primary delimiter in Forth, removing every carriage return would make no difference. Indentation, of course, does. )

## ( Commented: )

( Uses bit array, max 64 width on AMD64 with gforth. )

( Could shave an extra thirty or so bytes by not restoring )
( the numeric base, )
( and a few more by pulling frame and 0u.r into the definition. )

: newbase ( n -- oldbase )  ( swap base with n )
base @ swap base ! ;

: 0u.r ( u width -- )  ( unsigned numeric output, no leading zero suppression )
swap s>d rot <# 0 ?do # loop #> type ;

: frame ( n -- f )  ( frame )
1- 1 swap lshift 1 or ;

: %  ( n -- )  ( Make the % sign )
2 newbase swap ( Use binary output. )
cr dup frame . cr ( Frame the first line. )
2 over 2 -
dup 0< 0= if ( Are we already done? )
0 ?do ( Loop doesn't do the first or last. )
2dup swap 0u.r cr ( Zero fill, right justify. )
2*
loop
1 or . ( Put the second frame out. )
else
drop drop
then
cr
drop base ! ;


## ( Execution examples: )

1 %
1

ok
2 %
11
11
ok
3 %
101
010
101
ok
10 %
1000000001
0000000010
0000000100
0000001000
0000010000
0000100000
0001000000
0010000000
0100000000
1000000001
ok
40 %
1000000000000000000000000000000000000001
0000000000000000000000000000000000000010
0000000000000000000000000000000000000100
0000000000000000000000000000000000001000
0000000000000000000000000000000000010000
0000000000000000000000000000000000100000
0000000000000000000000000000000001000000
0000000000000000000000000000000010000000
0000000000000000000000000000000100000000
0000000000000000000000000000001000000000
0000000000000000000000000000010000000000
0000000000000000000000000000100000000000
0000000000000000000000000001000000000000
0000000000000000000000000010000000000000
0000000000000000000000000100000000000000
0000000000000000000000001000000000000000
0000000000000000000000010000000000000000
0000000000000000000000100000000000000000
0000000000000000000001000000000000000000
0000000000000000000010000000000000000000
0000000000000000000100000000000000000000
0000000000000000001000000000000000000000
0000000000000000010000000000000000000000
0000000000000000100000000000000000000000
0000000000000001000000000000000000000000
0000000000000010000000000000000000000000
0000000000000100000000000000000000000000
0000000000001000000000000000000000000000
0000000000010000000000000000000000000000
0000000000100000000000000000000000000000
0000000001000000000000000000000000000000
0000000010000000000000000000000000000000
0000000100000000000000000000000000000000
0000001000000000000000000000000000000000
0000010000000000000000000000000000000000
0000100000000000000000000000000000000000
0001000000000000000000000000000000000000
0010000000000000000000000000000000000000
0100000000000000000000000000000000000000
1000000000000000000000000000000000000001
ok


( Final note: works to one less than the bit width of the Forth interpreter. I ran the above on gforth, AMD64. An ancient 16-bit Forth would only go to 15 bits wide, and would need a bit of modification. )

• If you want to have the commented code in your answer that's fine, but you do need the golfed down code somewhere, too. – Pavel Jul 29 '17 at 5:42
• @Phoenix Thanks. Done. – Joel Rees Aug 1 '17 at 1:30

# C# (.NET Core), 65 bytes

w=>{var l=new int[w*w];for(int i=0;i<w*w;i+=w-1)l[i]=1;return l;}


Try it online!

The algorithm is significantly distinct from the other C# answer, so I decided to post it separately rather than as an improvement. Inspired by the top rated Jelly answer actually, I was doing something slightly less compact before. The output is a linear array, so would require some logic to wrap it into a 2D outside the method as-is. An alternate version requires 6 additional bytes to output as a true 2D array:

w=>{var l=new int[w,w];for(int i=0;i<w*w;i+=w-1)l[i/w,i%w]=1;return l;}


I also have an interesting non-competing version.

using System.Linq;w=>new int[w*w].Select((_,i)=>i%(w-1)<1)


This ends up with almost the right output, resulting in an IEnumerable<bool> with true/false instead of 1/0, and it's a linear rather than 2D structure, and although not needed for that exact line of code, using System.Collections.Generic is necessary to do anything useful with the output. Like I said, it's very close to being valid but not quite.

• For the second using a ternary as in ?1:0 works and I believe an array of the result should be fine. The collections using also isn't necessary for that code. – TheLethalCoder Aug 1 '17 at 15:24
• For the first, would setting w*w to a variable and moving the int declaration out of the loop save you anything? – TheLethalCoder Aug 1 '17 at 15:25
• @TheLethalCoder Replacing the two instances of w*w with a single character variable saves 4 bytes, moving int i=0 outside the loop requires a semicolon which costs 1 byte, and then adding ,s=w*w to the declaration costs 6 bytes, so it actually nets +3 bytes. – Kamil Drakari Aug 1 '17 at 15:36
• You should use the byte count of the full 2D-representation solution. The array returned by the shorter solution would at least need to include some sort of delimiter to be valid. – Jakob Aug 12 '17 at 3:37