Code Golf: Prime Factors of a Number [closed]

Answer 1

Erlang, the core is 122 chars and 152 for the whole module:

-module(pf).
-export([f/1]).

f(N) -> f(N,2,[]).
f(1,_,L) -> lists:reverse(L);
f(N,P,L) when N rem P == 0 -> f(N div P,P,[P|L]);
f(N,P,L) -> f(N,P+1,L).

To call from console:

70> string:join([integer_to_list(X) || X <- pf:f(1806046)], "x").
"2x11x11x17x439"

Answer 2

Euphoria: 106 characters

procedure f(atom a)atom x=2
loop do
while remainder(a,x)do
x+=1
end while
?x
a/=x
until a=1
end procedure

Answer 3

Javascript, 56

f="";
for(i=2;i<n;i++)
    if(n%i==0){
        f+=i+"x";
        n/=i;i--
    }
f+=n;

(54 characters)

first declare n= the number to be factored (2 characters included)

then execute the code.

example:

> n=12345
  12345

> f="";for(i=2;i<n;i++)if(n%i==0){f+=i+"x";n/=i;i--}f+=n
  "3x5x823"

Answer 4

The Go programming language, 100 characters:

package main;func main(){n:=42;c:="x";for i:=2;n>1;i++{if n%i<1{n/=i;if(n<2){c=""};print(i,c);i--}}}

My program, with the correct indentation:

package main

func main() {
 n := 42 // or whichever input number you like
 c := "x" // separating printed integers
 for i:=2 ; n>1; i++ {
  if n%i<1 { // n%i==0
   n /= i
   if(n<2) { c = "" } // n==1
   print(i, c)
   i--
  }
 }
}

Answer 5

In PARLANSE, this would do the trick (252 chars):

(action (procedure natural)
   (loop 
      (ifthen (== ? 1) (return))
      (do f i 2 ? 1
         (ifthen (== (modulo ? i) 0)
            (print ?)
            (= ? (/ ? i))
            (exit f)
         )ifthen
      )do
    )loop
)action

I'm sure there's a much smaller APL program to do this.

Answer 6

Mathematica (15 chars including brackets):

FactorInteger

Example:

FactorInteger[42]

{{2, 1}, {3, 1}, {7, 1}}