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):

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

Answer 1

Jolf, 7 bytes

This time, the builtin didn't let me win. Oh well.

―t0jj'*

Try it here!

Explanation

―t0jj'*
―t0     pattern: left-corner-base triangle
   j     with <input> height
    j    and <input> width.
     '*  comprised of asterisks

Answer 2

Racket 47 bytes

(for((i(+ 1 n)))(displayln(make-string i #\*)))

Ungolfed:

(define (f n)
  (for ((i (+ 1 n)))                         ; (i 5) in 'for' produces 0,1,2,3,4 
    (displayln (make-string i #\*))))        ; #\* means character '*'

Testing:

(f 5)

Output:

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

Answer 3

Java 7,72 70 bytes

Thanks to @kevin for shave it off by 2 bytes.

String f(int n,String s,String c){return n<1?c:f(--n,s+"*",c+s+"\n");}

Output

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

Answer 4

Ruby, 27 (or 24) bytes

(Thanks to m-chrzan for pointing out the miscounting.)

Returns a string.

->n{(1..n).map{|i|?**i}*$/}

the map makes an array of strings of * of increasing length. The *$/ takes the array and joins the elements to make a newline-separated string. If an array of strings is acceptable, these three bytes can be saved, scoring 24.

In test program

f=->n{(1..n).map{|i|?**i}*$/}
puts f[5]

Answer 5

C++, 78 bytes

I don't know how there are 2 C++ answers that don't just do it with for loops. Very short and sweet this way:

void T(int n){for(int i=1;i<=n;i++){for(int j=0;j<i;j++)cout<<'*';cout<<'\n';}}

Full program

#include <iostream>

using namespace std;

void T(int n)
{
    for(int i = 1; i <= n; i++)
    {
        for(int j = 0; j < i; j++)
            cout << '*';
        cout << '\n';
    }
}

int main()
{
  T(5);
}

Edit: it is unclear to me whether to count the #include<iostream>, using namespace std, and/or std::whatever in calls. C/C++ answers all over this site seem to use both, and for the most part no one seems to care except for the occasional comment. If I need the std::, then +10. If I need the #include<iostream>, +18 (although GCC allows me to do without the basic includes, so maybe not that one)

Answer 6

Java, 110 bytes

Not that short, but I really like having empty for loops.

String f(int n){String s="";for(int i=0;i<n;i++,s+=new String(new char[i]).replace("\0","*")+"\n"){}return s;}

Answer 7

GameMaker Language, 68 bytes

a="*"for(i=2;i<=argument0;i++){a+="#"for(j=0;j<i;j++)a+="*"}return a

Answer 8

Prolog, 60 58 56 bytes

g(N):-N<=0,put(*),g(N-1);!.
f(N):-N<=0,f(N-1),g(N),nl;!.

I'm not that familiar with Prolog, but I just gave it a shot. I'm sure it can be a lot shorter.

Put the code into a file, then load that file into swipl and run f(25). (or some other number).

EDIT: quotes can be left out in put statement
EDIT 2: changing =:= to <= saves 2 bytes. I tried inverting it, but that'd make it wait for a return for some reason.

Answer 9

Elixir, 81 bytes

&Enum.reduce(Enum.to_list(1..&1),"",fn(x,r)->r<>String.duplicate("*",x)<>"\n"end)

Anonymous function using the capture operator. Enum.reduce will iterate a list (the list is obtained by calling Enum.to_list on the range 1..n) and concatenate the return string r (which has been initialized with "") with a string made of x asterisks and a newline.

Full program with test case:

s=&Enum.reduce(Enum.to_list(1..&1),"",fn(x,r)->r<>String.duplicate("*",x)<>"\n"end)
IO.write s.(5)

Try it online on ElixirPlayground !

Answer 10

Pyth, 10 8 Bytes

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

VQ*Np"*"

Try it

Answer 11

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

Answer 12

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:

1. Output as many asterisks as necessary
2. Output a linefeed
3. Reset the value of the cell controlling the asterisks
4. Increment the control cell
5. Decrement the cell with the number until it equals 0

Answer 13

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:

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

Answer 14

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;

Answer 15

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:

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

Answer 16

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.

Answer 17

Dip, 6 5 bytes

`**En

-1 byte thanks to Oliver

Explanation:

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

Answer 18

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('*');}

Answer 19

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))

Answer 20

SmileBASIC, 30 bytes

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

Answer 21

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")

Answer 22

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

Answer 23

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.

Answer 24

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 \*

Answer 25

Terrapin logo, 67 bytes

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

Answer 26

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

Answer 27

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

Answer 28

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*/
}

Answer 29

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 30

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