Draw an asterisk triangle

Question

Inspired by a task for programming 101 here's a task that hopefully isn't too easy or is a duplicate (kinda hard to search for things like this).

Input:

A positive integer n >= 1.

Output:

n lines of asterisks, where every new line has one asterisk more than the line before, and starting with one asterisk in the first line.

General rules:

This is code-golf, so shortest answer in bytes wins.
Since the course is taught in C++, I'm eager to see solutions in C++.

Test case (n=5):

*
**
***
****
*****

\$\begingroup\$ Not duplicate, just subset of Generate a right triangle. \$\endgroup\$ – manatwork Oct 10 '16 at 12:20 — manatwork, Oct 10 '16 at 12:20
\$\begingroup\$ Training spaces allowed on each line? \$\endgroup\$ – Luis Mendo Oct 10 '16 at 12:33 — Luis Mendo, Oct 10 '16 at 12:33
\$\begingroup\$ Is a trailing new line acceptable? \$\endgroup\$ – Fatalize Oct 10 '16 at 12:34 — Fatalize, Oct 10 '16 at 12:34
\$\begingroup\$ Is a leading newline allowed? \$\endgroup\$ – Riley Oct 10 '16 at 14:38 — Riley, Oct 10 '16 at 14:38
\$\begingroup\$ I don't see a reason why not. \$\endgroup\$ – Sickboy Oct 11 '16 at 11:35 — Sickboy, Oct 11 '16 at 11:35

Connor D · Accepted Answer · 2016-10-13 16:40:44Z

2

Pyth, 10 8 Bytes

thanks to Jakube for helping me shave off the extra 2 bytes!

VQ*Np"*"

Try it

edited Oct 13 '16 at 16:40

answered Oct 10 '16 at 20:26

Connor D

813 bronze badges

\$\begingroup\$ FNU is the same thing as V. And you don't need that p, printing is implicit. \$\endgroup\$ – Jakube Oct 11 '16 at 15:54
\$\begingroup\$ without the p the code doesn't execute properly. It would print one less level than it should. \$\endgroup\$ – Connor D Oct 13 '16 at 16:39

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acrolith · Accepted Answer · 2016-10-15 00:27:15Z

2

Since the course is taught in C++, I'm eager to see solutions in C++.

C++, 123 bytes, Non-competing

(the joke here is to deliver a 'pure' c++ answer)

#include<string>
class X:public std::string{public:X(int i):std::string(i*(i+1)/2,'*'){for(;i--;)insert(i*(i+1)/2,"\n");}};

Test

edited Oct 15 '16 at 0:27

acrolith

3,7181 gold badge18 silver badges40 bronze badges

answered Oct 14 '16 at 22:20

user60119

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Anonymous No Lifer · Accepted Answer · 2016-10-20 18:36:57Z

Brainfuck, 129 bytes

I know there's already a shorter answer in brainfuck, however I wanted to create a program which could handle a multi-digit number input rather than either a single-digit input or a single ascii character input unlike the previous one posted.

,[>+++[->++++[-<<---->>]<]+>,]<-<<[<<]>>[<[->>++++++++++<<]>>>]+>>++++++++++>>++++++[-<+++++++>]<<<<<[>[->+>>.<<<]>>.<[-<+>]<+<-]

This is my first ever brainfuck program and it will work for any input between 0 and the maximum size of a single cell (traditionally 8 bits or 255) entered using the characters '0' to '9' (corresponding to ascii-values 048-057)

Explanation

The first part of this program, ,[>+++[->++++[-<<---->>]<]+>,], takes the input numbers as char values and removes 48 from each to make them equal to the numbers 0 to 9 rather than the char values of the numbers 0 to 9. It stores these in separate cells with a 1 in between each of them so that the start and end points can be found again.

The second part, <-<<[<<]>>[<[->>++++++++++<<]>>>], consolidates the separate values into one cell. This is why the maximum size of a cell controls how high a number can be.

The third section, +>>++++++++++>>++++++[-<+++++++>]<<<<<, is used to set up the other cells needed: one with the number of asterisks per line, one with the code for a linefeed and one with the code for an asterisk. There is also a blank cell left for working with later.

The remainder of the code, [>[->+>>.<<<]>>.<[-<+>]<+<-], is used to:

Output as many asterisks as necessary
Output a linefeed
Reset the value of the cell controlling the asterisks
Increment the control cell
Decrement the cell with the number until it equals 0

Geno Racklin Asher · Accepted Answer · 2016-10-24 15:48:37Z

05AB1E, 11 bytes

'*×.pD¦`r`»

Try it online!

Explanation: (Prints hourglass)

                  Implicit input - 5
'*                Asterisk character - stack = '*'
  ×               Repeat input times - stack = '*****'
   .p             Get prefixes       - stack = ['*', '**', '***', '****', '*****']
     D            Duplicate last element
                  STACK = ['*', '**', '***', '****', '*****'] , ['*', '**', '***', '****', '*****']
      ¦           Remove first element from final list
                  STACK = ['*', '**', '***', '****', '*****'] , ['**', '***', '****', '*****']
       `r`        Reverse 1 list and flatten both
                  STACK = '*****','****','***','**','*','**','***','****','*****'
          »       Join by newlines and implicitly print

For input 5, prints:

*****
****
***
**
*
**
***
****
*****

Karl Napf · Accepted Answer · 2016-10-25 11:59:23Z

2

C++ 11, 65 bytes

Not including the include in the byte count.

#include<string>
using S=std::string;S g(int n){return n?g(n-1)+S(n,'*')+'\n':"";}

Usage:

std::cout << g(n) << std::endl;

answered Oct 25 '16 at 11:59

Karl Napf

4,1117 silver badges28 bronze badges

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Pete Arden · Accepted Answer · 2016-10-26 13:51:22Z

2

SQL, 153 Bytes

Golfed:

CREATE PROCEDURE P @n INT AS BEGIN DECLARE @a INT;SET @a=0;DECLARE @o VARCHAR(1000);SET @o='*'WHILE @a<@n BEGIN PRINT @o;SET @o=@o+'*'SET @a=@a+1;END;END

Ungolfed:

CREATE PROCEDURE P
@n INT 
AS 
BEGIN 
DECLARE @a INT;
SET @a=0;
DECLARE @o VARCHAR(1000);
SET @o='*'
WHILE @a<@n
    BEGIN 
    PRINT @o;
    SET @o=@o+'*'
    SET @a=@a+1;
END;
END

Testing:

EXEC P '6'

Output:

*
**
***
****
*****
******

edited Oct 26 '16 at 13:51

answered Oct 26 '16 at 13:38

Pete Arden

1,1514 silver badges9 bronze badges

1

\$\begingroup\$ Wow, that's awesome! :-) \$\endgroup\$ – Sickboy Oct 27 '16 at 7:41
\$\begingroup\$ @Sickboy thanks! :) My language of choice is normally C#, but someone beat me to it! :) \$\endgroup\$ – Pete Arden Oct 27 '16 at 9:22
\$\begingroup\$ just @ is also a legal variable name in SQL, might save a couple of bytes there, and you can set the variable values directly in the DECLARE like so DECLARE @a INT=0 and a lot of those ; are unnecessary \$\endgroup\$ – grabthefish Feb 20 '17 at 14:31
\$\begingroup\$ also VARCHAR(MAX) is 1 shorter \$\endgroup\$ – grabthefish Feb 20 '17 at 14:33

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Zatherz · Accepted Answer · 2016-10-26 21:04:54Z

Crystal, 31 bytes

n=5;(1..n).each{|x|puts "*"*x}

Output:

*
**
***
****
*****

Really demonstrates the beauty of Crystal/Ruby. n is the integer input, (1..n) is an inclusive range from 1 to n ([1, n]). .each is a method on Range that runs the provided block for every integer in the range.

Community · Accepted Answer · 2017-04-13 12:39:16Z

2

Dip, 6 5 bytes

`**En

-1 byte thanks to Oliver

Explanation:

`**    Push "*" repeated input times
   E   Prefixes
    n  Join by newlines

edited Apr 13 '17 at 12:39

Community♦

1

answered Oct 26 '16 at 19:29

acrolith

3,7181 gold badge18 silver badges40 bronze badges

\$\begingroup\$ 5-byte version: ``**En` \$\endgroup\$ – Oliver Ni Oct 30 '16 at 16:55

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score 2 · Accepted Answer · 2016-10-31 16:03:03Z

C, 88 bytes / 53 bytes

Using C89.

g(a){a&&g(a-1);a<2||puts("");while(a--)putchar('*');}main(int a,char**v){g(atoi(v[1]));}

With whitespace for clarity:

g(a) {
    a && g(a-1);
    a<2 || puts("");
    while (a--) putchar('*');
}
main(int a, char** v) {
    g(atoi(v[1]));
}

Without main, this function is 53 bytes:

g(a){a&&g(a-1);a<2||puts("");while(a--)putchar('*');}

Elronnd · Accepted Answer · 2016-11-01 02:03:14Z

2

python3, 58 57 bytes

print('\n'.join(['*'*(p+1)for p in range(int(input()))]))

Ungolfed:

rownums = int(input())
output = []
for i in range(rownums):
    currrow = "*" * (i+1) # 'i' * 5 == 'iiiii'
    output.append(currrow)
print('\n'.join(output))

edited Nov 1 '16 at 2:03

answered Oct 30 '16 at 21:37

Elronnd

1017 bronze badges

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12Me21 · Accepted Answer · 2017-02-09 16:19:31Z

2

SmileBASIC, 30 bytes

INPUT N
FOR I=1TO N?"*"*I
NEXT

answered Feb 9 '17 at 16:19

12Me21

6,0601 gold badge13 silver badges36 bronze badges

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brander · Accepted Answer · 2017-02-11 19:52:57Z

2

Haskell 36 Bytes

Here is a version using map.

f="*":map('*':)f;g=unlines.(`take`f)

Input g 10 Output "*\n**\n***\n****\n*****\n******\n*******\n********\n*********\n**********\n"

Alternatives of interest might be:

38 Bytes

g n=id=<<scanl(\x y->'*':x)"*\n"[2..n]

38 Bytes

f="*\n":map('*':)f;g n=id=<<(n`take`f)

36

g n=id=<<(take n$iterate('*':)"*\n")

edited Feb 11 '17 at 19:52

answered Feb 11 '17 at 17:37

brander

1113 bronze badges

\$\begingroup\$ Anonymous functions are allowed, so you don't need the g=. \$\endgroup\$ – Laikoni Feb 11 '17 at 22:01

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Paul Kerrigan · Accepted Answer · 2017-02-22 16:24:18Z

2

k, 18 bytes

{-1@(1+!x)#\:"*";}

Explanation:

-1@ // prints to console

1+!x //returns list from 1 to x (implicit input)

#\:  //for each item in the prefixed list, "take" this many

"*" //asterisk string

answered Feb 22 '17 at 16:24

Paul Kerrigan

1895 bronze badges

1

\$\begingroup\$ @ isn't necessary, and you can use ' instead of \: for -2 bytes {-1(1+!x)#'"*";} \$\endgroup\$ – Thaufeki Nov 4 '18 at 5:32

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smls · Accepted Answer · 2017-02-22 17:15:15Z

Perl 6, 17 bytes

put(\*x++$)xx get

Full program that prints to stdout.
How it works:

    \*             # a Capture object that stringifies to the asterisk,
      x            # string-repeated by
       ++$         # a counter that starts at 1,
put(      )        # and printed followed by a newline.
           xx get  # Do all of that n times.

Invokes the put statement n times, each time printing the asterisk repeated by the counter variable ++$.

Perl 6, 21 bytes

{.put for \*Xx 1..$_}

A lambda that prints to stdout.
How it works:

{                   }  # A lambda.
          \*           # A Capture object that stringifies to the asterisk.
               1..$_   # Range from 1 to n.
            X          # Cartesian product of the two,
             x         # with the string repetition operator applied to each result.
 .put for              # Iterate over the strings, and print each followed by a newline.

Mitchell Spector · Accepted Answer · 2017-02-25 02:19:41Z

Bash + Unix utilities, 26 bytes

seq -f10^%f-1 $1|bc|tr 9 *

Output to stderr should be ignored.

Try it online!

The code above works on TIO since the working directory there has no visible files. If this needs to run in a directory that contains a visible file, change * to \* at the cost of one byte (27 bytes):

seq -f10^%f-1 $1|bc|tr 9 \*

Adrian Zhang · Accepted Answer · 2017-02-26 04:15:18Z

2

Terrapin logo, 67 bytes

to a :a
make "b 1 repeat :a[repeat :b[type "*]make "b b+1 pr "]
end

answered Feb 26 '17 at 4:15

Adrian Zhang

1991 silver badge5 bronze badges

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aross · Accepted Answer · 2017-03-03 15:55:30Z

2

PHP, 43 34 31 28 bytes

Note: uses IBM 850 encoding (old favorite reinvented recently)

for(;$argn--;)echo$o.=~ı,~§;

Run like this:

echo 5 | php -nR 'for(;$argn--;)echo$o.=~ı,~§;';echo
> *
> **
> ***
> ****
> *****

Explanation

Iterates from N down to 0. Add an asterisk to $o for each iteration, then outputs $o and a newline.

Tweaks

Add an asterisk to $o for each iteration, and then output $o. Saves 9 bytes
Combined adding an asterisk to $o with outputting, saves 3 bytes
Saved 3 bytes by using $argn

edited Mar 3 '17 at 15:55

answered Oct 10 '16 at 14:19

aross

1,5836 silver badges12 bronze badges

\$\begingroup\$ @TheBitByte, does my answer qualify for your bounty? It yields an asterisk by binary negation of ı (in IBM-850 encoding, as noted) \$\endgroup\$ – aross Oct 17 '16 at 8:36
\$\begingroup\$ Well, as long as it's an actual asterisk, then fine, it does qualify, however it is longer than some other bounty answers here. \$\endgroup\$ – Buffer Over Read Oct 19 '16 at 18:41

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Chromozorz · Accepted Answer · 2017-03-06 02:08:38Z

K, 16 Bytes

 {-1(1+!x)#'"*"};

  {-1(1+!x)#'"*"}10;
* 
**
***
****
*****
******
*******
********
*********
**********

EDIT BELOW - adding explanation)

/Code     ---> explanation (pretend x is 3)
1+!x      ---> Numbers from 1 to 3
1 2 3#"*" ---> Take left many items of right ==> ("*";"**";"***")
-1x       ---> Print x to the console, if x is a list, each item is printed to a new line

example(notice the -1 printed at the bottom). 
     -1("*";"**";"***")
     *
     **
     ***
     -1
To silence the output(-1), put a semicolon after the expression e.g.
-1("Hello");
Hello

Community · Accepted Answer · 2017-04-13 12:39:13Z

2

Röda 0.12, 30 29 bytes, non-competing

h i{seq 1,i|{|j|print"*"*j}_}

This is my first try in this scripting language created by fergusq :D

This is a function. To run, use this:

h i{seq 1,i|{|j|print"*"*j}_}

main {
  h(5)
}

Ungolfed

h i{                         /* Define a function h with parameter i */
   seq 1,i                   /* Generate a sequence of numbers from 1 to i */
          |{             }_  /*  and pipe it to a for-loop */
            |j|              /*  where j is the number in the sequence*/
               print"*"*j    /*  and print an asterisk duplicated j times*/
}

edited Apr 13 '17 at 12:39

Community♦

1

answered Mar 6 '17 at 18:48

Kritixi Lithos

15.6k5 gold badges30 silver badges78 bronze badges

\$\begingroup\$ The ; after the anonymous function parameter list is not actually required in Röda 0.12. It's a bug in the interpreter, but since you've specified the answer to be 0.12, I think you can remove it. I have been thinking that I may let the bug be, as its a handy feature in code golf, but haven't decided anything yet. \$\endgroup\$ – fergusq Mar 7 '17 at 13:32
\$\begingroup\$ @fergusq Thanks for the tip! "It's not a bug, it's a feature!" \$\endgroup\$ – Kritixi Lithos Mar 7 '17 at 14:38

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score 2 · Accepted Answer · 2017-07-21 13:21:21Z

2

Common Lisp, SBCL, 69 66 61 45 44 41 bytes

full program:

(dotimes(i(read))(format t"~v{*~}*
"i 1))

Explanation

(dotimes(i(read)) <-- loop from i=0 to i=INPUT-1
(format t"~v{*~}*
"i 1)) <-- loop, displaying i+1 asterisks per line

Ideas for improvement are welcomed.

edited Jul 21 '17 at 13:21

answered Feb 9 '17 at 13:01

user65167

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steenbergh · Accepted Answer · 2017-09-19 08:02:36Z

QBIC, 16 bytes

:#*|[1,a|B=B+A?B

Explanation:

:         Gets a cmd line param as number called 'a'
#*|       Define A$ as '*'
[1,a|     FOR b = 1 to a
B=B+A     Extend B$ with another astrix
?B        Print B$
<FOR LOOP implicitly closed>

QBIC's seen a few updates since this answer was posted. This could now be done with these 12 bytes:

[:|B=B+@*`?B

Taylor Scott · Accepted Answer · 2017-12-28 20:42:40Z

2

Excel VBA, 32 Bytes

Anonymous VBE immediate window function that takes input from range A1 and outputs to the VBE immediate window.

For i=1To[A1]:?String(i,42):Next

answered Dec 28 '17 at 20:42

Taylor Scott

6,5991 gold badge14 silver badges42 bronze badges

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ngn · Accepted Answer · 2018-01-13 21:51:21Z

2

APL (Dyalog Unicode), 7 bytes^SBCS

(,⍕⊢)⌸⍳

Try it online!

answered Jan 13 '18 at 21:51

ngn

10.8k1 gold badge29 silver badges67 bronze badges

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dzaima · Accepted Answer · 2018-01-14 11:15:58Z

2

Canvas, 3 bytes

*×］

Try it here!

Explanation:

  *×］  full program
｛  ］  map over [1..input]
  *×      repeat by *

answered Jan 14 '18 at 11:15

dzaima

18.5k2 gold badges28 silver badges66 bronze badges

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zgrep · Accepted Answer · 2018-04-11 02:37:53Z

2

k, 16 12 bytes

4 bytes removed thanks to ngn! :)

{`0:,\x#"*"}

{          } /function(x)
      x#"*"  /reshape "*" by x
    ,\       /scan concatenation through the list
 `0:         /print line by line

edited Apr 11 '18 at 2:37

answered Feb 26 '17 at 7:02

zgrep

1,2814 silver badges9 bronze badges

1

\$\begingroup\$ (1+!x)#'"*" -> ,\x#"*" \$\endgroup\$ – ngn Jan 13 '18 at 22:12

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Oliver · Accepted Answer · 2018-12-18 18:31:41Z

2

Japt `-R`, 8 4 bytes

õ_î*

Try it online!

4-byte alternative:

°Tî*

Try it online

edited Dec 18 '18 at 18:31

answered Feb 25 '17 at 3:15

Oliver

7,0802 gold badges10 silver badges36 bronze badges

1

\$\begingroup\$ You know, instead of adding a newline to every line, joining with spaces and trimming, you could just join with newlines ;-) \$\endgroup\$ – ETHproductions Feb 27 '17 at 14:56
\$\begingroup\$ Could you use this 5 byte version? \$\endgroup\$ – Shaggy Jun 19 '17 at 12:18

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manatwork · Accepted Answer · 2016-10-10 12:29:13Z

1

Gema, 36 characters

*=@repeat{*;@append{s;\*}@out{$s\n}}

Sample run:

bash-4.3$ gema '*=@repeat{*;@append{s;\*}@out{$s\n}}' <<< 5
*
**
***
****
*****

answered Oct 10 '16 at 12:29

manatwork

17.3k4 gold badges39 silver badges73 bronze badges

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mbomb007 · Accepted Answer · 2016-10-10 13:43:15Z

1

Forth, 39 bytes

Quite simple, with a couple of nested loops. ASCII 42 is an asterisk.

: f 0 do I -1 do 42 emit loop CR loop ;

Try it online

Prints a trailing newline.

answered Oct 10 '16 at 13:43

mbomb007

21.8k5 gold badges48 silver badges120 bronze badges

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manatwork · Accepted Answer · 2016-10-10 13:57:13Z

1

Bash, 35 characters

for((;i++<$1;));{ s+=\*;echo "$s";}

Sample run:

bash-4.3$ bash draw-an-asterisk-triangle.sh 5
*
**
***
****
*****

answered Oct 10 '16 at 13:57

manatwork

17.3k4 gold badges39 silver badges73 bronze badges

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John Doe · Accepted Answer · 2016-10-10 14:40:43Z

1

C++, 108 chars

#import<iostream>
main(){int n;std::cin>>n;for(int i=1;i<=n;++i){for(int j=i;j--;)std::cout<<"*";puts("");}}

Straightforward.

Try it online

edited Oct 10 '16 at 14:40

answered Oct 10 '16 at 14:28

John Doe

1115 bronze badges

\$\begingroup\$ Can the < be moved directly next to the #include? (I don't do C++, just a wild guess based on Java knowledge) \$\endgroup\$ – Addison Crump Oct 10 '16 at 14:30
\$\begingroup\$ You're right.__ \$\endgroup\$ – John Doe Oct 10 '16 at 14:31
1

\$\begingroup\$ The #include does need to be included in the byte count. \$\endgroup\$ – mbomb007 Oct 10 '16 at 14:39
\$\begingroup\$ Thanks for the C++ solution, but there's a shorter one ;-) \$\endgroup\$ – Sickboy Oct 11 '16 at 11:33

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Draw an asterisk triangle

134 Answers 134

Pyth, 10 8 Bytes

C++, 123 bytes, Non-competing

05AB1E, 11 bytes

C++ 11, 65 bytes

SQL, 153 Bytes

Crystal, 31 bytes

Dip, 6 5 bytes

C, 88 bytes / 53 bytes

python3, 58 57 bytes

SmileBASIC, 30 bytes

k, 18 bytes

Perl 6, 17 bytes

Perl 6, 21 bytes

Bash + Unix utilities, 26 bytes

Terrapin logo, 67 bytes

PHP, 43 34 31 28 bytes

Explanation

Tweaks

K, 16 Bytes

Röda 0.12, 30 29 bytes, non-competing

Ungolfed

Common Lisp, SBCL, 69 66 61 45 44 41 bytes

Explanation

QBIC, 16 bytes

Excel VBA, 32 Bytes

APL (Dyalog Unicode), 7 bytesSBCS

Canvas, 3 bytes

k, 16 12 bytes

Japt -R, 8 4 bytes

Gema, 36 characters

Forth, 39 bytes

Bash, 35 characters

C++, 108 chars

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