Multiply a string by a number!

Question

There was a challenge up a while ago about multiplying strings. It showed us how we can multiply not only numbers, but also strings. However, we still can't multiply a number by a string properly. There has been one attempt to do so but this is obviously wrong. We need to fix that!

Your Task:

Write a function or program that multiplies two inputs, a string and an integer. To (properly) multiply an string by an integer, you split the string into characters, repeat each character a number of times equal to the integer, and then stick the characters back together. If the integer is negative, we use its absolute value in the first step, and then reverse the string. If the input is 0, output nothing (anything multiplied by 0 equals nothing).

Input:

A string that consists solely of printable ASCII characters and newlines, and an integer (possible negative).

Output:

The string multiplied by the integer.

Examples:

Hello World!, 3            --> HHHeeellllllooo   WWWooorrrlllddd!!!
foo, 12                    --> ffffffffffffoooooooooooooooooooooooo
String, -3                 --> gggnnniiirrrtttSSS
This is a fun challenge, 0 --> 
Hello
World!, 2                  --> HHeelllloo

                               WWoorrlldd!!

Scoring:

This is code-golf, lowest byte count wins!

Answer 1

Forth, 132 bytes.

My first golf, Idk what I'm doing I'm sure it could be improved a lot.

: Z chars + c@ emit ; : X 0 do dup n Z loop ; : Y dup 0 < if negate then dup 0 > if n count 0 do over i 1 + swap X drop loop then ;

or

: Z chars + c@ emit ;
: X 0 do dup n Z loop ;
: Y dup 0 < if negate then dup 0 > if n count 0 do over i 1 + swap X drop loop then ;

The negate and comparisons are just for the 0 and negative cases. This is assuming we've already been given the string at 'n', I'm unsure if this is allowed.

Answer 2

QBIC, 32 bytes

g=sgn(c)[_l;||[:*g|?_sA,b*g,1|';

Explanation

            Takes inputs A$ ('Hello'), and c (-3) from the cmd line
g=sgn(c)    Save the sign of c          -1
[_l;||      FOR each char in A$
[:*g|       FOR the number of repetitions wanted    (ie: -3 * -1)
            Note that : reads a number from the cmd line, and c is the first 
            available variable to save it in after a and b got used as FOR counters.
            Also note that a negative value times the sign becomes positive.
?_s         PRINT a substring
  A         of A$
 ,b*g       startng at char n, where n is the first FOR loop counter times the sign
                That means that when c is negative, so is this. A negative starting index
                on Substring instructs QBIC to take from the right.
 ,1|        taking 1 char.
';          This bit injects a literal ; in the output QBasic, to suppress newlines om PRINT

Answer 3

Mathematica, 89 bytes

(T=Table;t=""<>T[s[[i]]~T~Abs@#2,{i,Length[s=Characters@#]}];If[#2>0,t,StringReverse@t])&

input

["Hello World!", 3]

Answer 4

Braingolf, 22 bytes

1-v{R.[v.R]v}R[v>R]v&@

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Eeh, not bad.

Takes input as an integer and an array of characters.

Alternatively:

Braingolf, 31 bytes

l1->[M]1-v&,{R.[v.R]v}R[v>R]v&@

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Takes input as an integer and a string

Answer 5

C, 109 bytes

char *f(int n, char *s){char *o=calloc(n,strlen(s)+1),*t=o;while(*s){for(int i=n;i--;)*t++=*s;s++;}return o;}

Starting with a function declaration that takes an int and a string and produces a string (it seems implied that memory is not preallocated and must be created) it seems that the straight-forward approach is shorter than any attempts at being cleaver that I had tried.

char *f(int n, char *s){
  char *o=calloc(n, strlen(s)+1),
    *t=o;

  while (*s) {
    for(int i=n; i--; )
      *t++=*s;
    s++;
  }

 return o;

}

Answer 6

Julia, 44 bytes

(s,x)->for i in split(s,"") print(i^abs(x))end

Answer 7

K/Kona, 19 18 bytes

{,/$[y>0;;|:]y#'x}

Now, in the 0 case, it does output something, but that's the empty string so I'm sure that's all gravy.

I actually missed the negative input part of this initially, which cost me eleven bytes! Definitely not my best work

Usage:

k){,/$[y>0;;|:]y#'x}["Hello World";3]
"HHHeeellllllooo   WWWooorrrlllddd!!!"
k){,/$[y>0;;|:]y#'x}["Hello World!";0]
""
k){,/$[y>0;;|:]y#'x}["String";-3]
"gggnnniiirrrtttSSS"

Answer 8

PowerShell, 89 bytes

param($s,$n)-join($s[((0..($L=$s.Length)),(-1..-$L))[$n[0]-eq45]]|%{"$_"*"$n".trim('-')})

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Generates a list of characters in the string, either forward or reversed, string-multiplies each, and joins the resulting array. $n[0]-eq45 is the ASCII code of - and .Trim('-') is shorter than [Math]::Abs($n)

Answer 9

C#, 70 Bytes

using System.Linq;(s,n)=>string.Join("",s.Select(c=>new string(c,n)));

The select function is used to create a new string with the original character repeated n-times, results are joined together.

Answer 10

C#, 108 bytes

using System.Linq;s=>n=>{var a=s.Select(c=>new string(c,n>0?n:-n));return string.Concat(n<0?a.Reverse():a);}

Full/Formatted Version:

using System;
using System.Linq;

namespace TestBed
{
    class Program
    {
        static void Main(string[] args)
        {
            Func<string, Func<int, string>> f = s => n =>
            {
                var a = s.Select(c => new string(c, n > 0 ? n : -n));

                return string.Concat(n < 0 ? a.Reverse() : a);
            };

            Console.WriteLine(f("Hello World!")(3));
            Console.WriteLine(f("foo")(12));
            Console.WriteLine(f("String")(-3));
            Console.WriteLine(f("This is a fun challenge")(0));
            Console.WriteLine(f(@"Hello
World!")(2));

            Console.ReadLine();
        }
    }
}

Answer 11

Brainfuck, 26 bytes

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

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Answer 12

vim, 45 bytes

:s/\(.\)/\1<C-v>
/g
adl<esc>gJaP<esc>"add
:%norm @a
:%j!

<esc> is 0x1b, and <C-v> is 0x16.

:s/\(.\)/\1<C-v><nl>/g splits the string into one character per line.

adl<esc>gJaP<esc>"add then constructs a command in buffer a that will copy a line n times, where n is the number that was previously on this line.

%norm @a and :%j! then apply that command to each line in the file and rejoin the lines respectively.

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Answer 13

C++, 152 bytes

#define l(x,n)for(int x=0;x<n;++x)
typedef std::string s;s f(s t,int c){s r;l(i,t.size())l(j,abs(c))r+=t[i];if(c<0)reverse(r.begin(),r.end());return r;}

And here's the full code you can test with.

#include <iostream>

#define l(x,n)for(int x=0;x<n;++x)
typedef std::string s;s f(s t,int c){s r;l(i,t.size())l(j,abs(c))r+=t[i];if(c<0)reverse(r.begin(),r.end());return r;}

int main(int argc, const char * argv[]) {
    std::cout << f("Hello World!", 3) << std::endl;
    std::cout << f("foo", 12) << std::endl;
    std::cout << f("String", -3) << std::endl;
    std::cout << f("This is a fun challenge", 0) << std::endl;
    std::cout << f("Hello\nWorld!", 2) << std::endl;
    return 0;
}

Answer 14

Unwanted, Unnecessary, Opportunistic, 7 bytes

IAM*|V^

Answer 15

Clojure, 24 bytes

#(for[c % _(range %2)]c)

Returning a string instead of a sequence of characters pushes this to 35 bytes:

#(apply str(for[c % _(range %2)]c))

Answer 16

[C#], 103 bytes

var r=n<0?-n:n;var a=new int[p.Length*r].Select((_,i)=>p[i/r]);return String.Concat(n<0?a.Reverse():a);

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Tried something a little different from the other C# answers, without using 'new string(str, x)'.

Answer 17

Vyxal, 7 bytes

ȧ•?0<[Ṙ

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There's gotta be a better way to do this.

 •      # Repeat each char by...
ȧ       # absolute value of input
  ?0<[  # If it's negative
      Ṙ # Reverse

Answer 18

><> (Fish), 61 bytes

:&0)?v>i:0(?^\
-$0&0/\p3a'r'&
 .07~v?:<+1&:/
{:}+1/ >o< ~\.28

Try it

Explanation

Takes the number as the initial stack value, and the string as the STDIN.

Uses source code modification: Inserts a r command at 10,3 if the number is positive. If so invert the number. The & instruction is nicely in the perfect place both from the top and from the right side.

The {:} copies the character -n times.

Answer 19

Thunno 2, 7 bytes

AḄ$0<?r

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Explanation

AḄ$0<?r  # Implicit input
 Ḅ       # Multiply each character of the second input by...
A        # ...the absolute value of the first input
  $      # Push the first input again
   0<    # And check if it's negative
     ?   # If it is negative:
      r  #  Reverse the string
         # Implicit output

Answer 20

Mathematica, 56 bytes

""<>Thread@Table[Reverse[Characters@#2,2+Sign@#],Abs@#]&

Try it at the Wolfram sandbox! (Doesn't work in Mathics…)

Takes the number then the string as input.

The Reverse function can take a second parameter saying what level of the array to reverse at (so Reverse[{{1,2},{3,4}}] returns {{3,4},{1,2}} but Reverse[{{1,2},{3,4}},2] gives {{2,1},{4,3}}, for instance). When the input number is negative, we reverse at level 1, but when it's zero or positive, we reverse at level 2 or 3. Since Characters@#2 is a list with only one level, reversing at deeper levels has no effect.

Once that's done, we repeat the list of characters then transpose the resulting array using Thread so the repeated characters end up next to each other.

Answer 21

tcl, 120

proc M s\ n {if $n<0 {set s [string rev $s];set n [expr -$n]};lmap c [split $s ""] {append x [string repe $c $n]};set x}

demo

Answer 22

Retina, 76 bytes

Os^$`(?<=^-.+¶.*).

^.+
$*
s`(?<=¶.*)
	
{`^1

}s`(?<=^1.*)	(.)
	$1$1
\`^¶|	

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Answer 23

Husk, 13 bytes

So?I↔>0o`ȯṁRa

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Ungolfed/Explanation

       o`ȯṁ    -- with the input string..
           Ra  -- ..multiply each character by the absolute value |N|
So?            -- depending on N either apply..
   I           -- ..the identity..
     >0        -- ..if N>0 or else..
    ↔          -- ..reverse it

Answer 24

C (gcc), 80 bytes

i;L;f(s,n)char*s;{L=strlen(s);for(i=0;i*i<L*n*L*n;)putchar(s[i++/n+~-L*(n<0)]);}

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-1 byte from ceilingcat

Answer 25

Raku, 50 bytes

{($^a.comb »x»$^b.abs).join.&{$b <0??.flip!!$_}}

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Answer 26

JavaScript (Node.js), 61 bytes

n=>g=(h,i=n,[c,...x]=h)=>c?i?i>0?c+g(h,i-1):g(h,i+1)+c:g(x):h

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No longer longer than Q256411, but even same length it's only

Answer 27

Japt -P, 10 bytes

ÆVÃÕzUÌÉ©2

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ÆVÃÕzUÌÉ©2     :Implicit input of integer U & string V
Æ              :Map the range [0,U)
 V             :  Return V
  Ã            :End map
   Õ           :Transpose
    z          :Rotate clockwise this many times
     UÌ        :  Sign of difference between U & -1
       É       :  Subtract 1
        ©2     :  Logical AND with 2
               :Implicitly join & output