Draw an asterisk triangle

Question

Inspired by a task for Programming 101, here's a challenge that hopefully isn't too easy (or a duplicate).

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.

Test case (n=5):

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

This is code-golf, so shortest answer in bytes wins.

Answer 1

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.

Answer 2

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

Answer 3

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

Answer 4

Canvas, 3 bytes

*×］

Try it here!

Explanation:

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

Answer 5

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

Answer 6

Japt -R, 8 4 bytes

õ_î*

Try it online!

4-byte alternative:

°Tî*

Try it online

Answer 7

Wren, 41 bytes

Fn.new{|i|(1..i).map{|n|"*"*n}.join("
")}

Try it online!

Explanation

Fn.new{|i|                             // New function with the parameter i
          (1..i)                       // Generate a range from 1 to i
                .map{|n|"*"*n}         // Replace the numbers with asterisks
                              .join("
")}                                    // Join with newline

Answer 8

MathGolf, 4 bytes

╒⌂*n

Try it online or verify some more test cases.

Explanation:

╒     # Push a list in the range [1, (implicit) input]
 ⌂    # Builtin for the asterisk character "*"
  *   # Map each value to that amount of asterisk characters (similar as in Python)
   n  # And join this list of strings by newlines
      # (after which the entire stack joined together is output implicitly as result)

Answer 9

SNOBOL4 (CSNOBOL4), 59 52 bytes

	n =input
o	output =o =o '*' lt(size(o),n) :s(o)
end

Try it online!

Answer 10

C++ (gcc), 61 bytes

int f(int n){for(n&&f(n-1);~n;__builtin_putchar(n--?42:10));}

Uses ASCII char codes and builtins to shorten another solution.

Try it online!

Answer 11

J, 8 bytes

[\@$&'*'

Explanation:

1. $&'*': Reshape * according to.

• $: Reshape.
• &: Bound with (partial application).
• '*': Character literal *.

2. @: Function composition.

3. [\: Each prefix of.

• [: Identity.
• \: Apply the preceding verb to each prefix of the right argument.

Answer 12

Vyxal j, 3 bytes

×*¦

Try it Online!

How?

×*¦
×*  # Repeat an asterisk the implicit input amount of times
  ¦ # Prefixes
    # j flag joins on newlines

Answer 13

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

C++, 123 bytes

(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

Answer 14

Gema, 36 characters

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

Sample run:

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

Answer 15

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.

Answer 16

Bash, 35 characters

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

Sample run:

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

Answer 17

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

Answer 18

Vitsy, 19 16 bytes

Yeah this needs some reducing. I'm out of practice!

D1H}\[\['*'O]aO]

(implicit input)
D                 Peek n, push n.
 1                Push 1.
  H               Pop x, pop y, push range(x, y)
   }              Reverse, pop n, reverse, push n.
    \[         ]  Pop n, do bracketed items n times.
      \[    ]     Pop n, do bracketed items n times.
        '*'O      Output the character *.
             aO   Output a newline.

Think of it as though I'm iterating through a list (1 through n) and popping out the number of *s according to the currently selected list item.

Explanation soon.

Answer 19

Clojure, 59 bytes

#(doseq[m(range 1(inc %))](println(apply str(repeat m\*))))

Basically, just uses doseq to loop over the range, printing the corresponding number of stars.

It's really unfortunate that the shortest way I've been able to repeat a character in Clojure is (apply str (repeat m \*)). That's hardly competitive here. Some good ol' python string multiplication would have been awesome.

Ungolfed:

(defn tri [n]
  (doseq [m (range 1 (inc n))]
    (println (apply str (repeat m \*)))))

Should be fairly self-explanatory.

Answer 20

Befunge93, 31 chars (3 spaces, 8 pure directionals)

&>:#v_@
-^  : >$55+,1
,"*"<_^#:-1

Befunge98, 28 chars

&>:#v_@
-^  : >$a,1
1,*'<_^#:-

Answer 21

Ruby, 32 bytes

1.upto($*[0].to_i){|i|puts"*"*i}

The $* is an array of arguments.

foo.rb 5 will print the following:

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

Answer 22

Excel VBA, 109 bytes

This function returns to cell, requires text wrapping be turned on.

Function a(b)
For i = 1 To b
For c = 1 To i
d = "*" & d
Next c
a = a & d & Chr(10)
d = ""
Next i
End Function

99 Bytes - Alternative that runs as a function but prints to immediate.

Function f(b)
For i = 1 To b
For c = 1 To i
Debug.Print "*";
Next c
Debug.Print
Next i
End Function

94 Bytes - One more that is just a sub with hard coded value, prints to immediate.

Sub k()
r = 5
For i = 1 To r
For c = 1 To i
Debug.Print "*";
Next c
Debug.Print
Next i
End Sub

Answer 23

PHP, 66 58 bytes

Just a simple loop, really.

I'm new to golfing, so might not be the shortest way.

for($i=fgets(STDIN);$x++<$i;)echo str_repeat("*",$x)."\n";

https://eval.in/658719

^{Thanks to manatwork for byte-saving.}

Answer 24

Javascript, 71 bytes 48 Bytes, thanks ETHproductions!

(n,c)=>{while(c<=n)console.log("*".repeat(c++))}

Answer 25

Ruby, 29 bytes

->n{n.times{|i|puts'*'*i+?*}}

Call with ->n{n.times{|i|puts'*'*i+?*}}[number].

Answer 26

VBA, 84 bytes

taking advantage of recursive coding. it generates x times * as the line/round

Function f(x)
If x<=1 Then f="*" Else f=f(x-1) & vbCrLf & String(x,"*")
End Function

results:

?f(10)
*
**
***
****
*****
******
*******
********
*********
**********
?f(2)
*
**

?f(5)
*
**
***
****
*****

Answer 27

Common Lisp (Lispworks), 71 bytes

(defun f(n)(dotimes(i n)(dotimes(j(1+ i))(format t"*"))(format t"~%")))

Usage:

CL-USER 170 > (f 5)
*
**
***
****
*****
NIL

Ungolfed:

(defun f (n)
  (dotimes (i n)
    (dotimes (j (1+ i))
      (format t "*"))
    (format t "~%")))

Answer 28

MoonScript, 31 bytes

(n)->for i=1,n
 print "*"\rep i

Sample call:

_ 5

Answer 29

F#, 114 chars

[<EntryPoint>]
let main a =
 for i = 1 to System.Int32.Parse(a.[0]) do
  printfn "%s" <| String.replicate i "*"
 0

Answer 30

Braingasm, 27 bytes

Braingasm is a brainfuck variant with just a few more instructions and options. And this task would've been so much easier if I had bothered implementing that as many times as the value in the current cell thing yet..

;[->+[->+42.<]10.>[-<+>]<<]

Here's how it works:

;                           Read an integer from stdin and write it to cell#1
 [                        ] While the value of cell#1 is not zero,
  ->+                    <    substract one from cell#1 and add one to cell#2.
     [->+   <]                Each time, do the same between cell#2 and cell#3,
         42.                    but also print an asterix on the way.
              10.             Then print a newline.
                 >[-<+>]<     Move the value from cell#3 back to cell#2