Code Golf: Prime Factors of a Number [closed]

Answer 1

In a similar vein as Paxinum (Mathematica answer), here's one in bash:

$ factor 1806046
1806046: 2 11 11 17 439

7 characters the excluding number.

Answer 2

Obligatory J answer (2 characters):

q:

Answer 3

VB6/VBA - 190 chars

Public Function P(N As Long) As String
Dim I As Long, O As String
Do While N > 1: For I = 2 To N
If N Mod I = 0 Then
O = O & " " & I: N = N / I: Exit For: End If: Next: Loop: P = O: End Function

Answer 4

VB6/VBA - 147 chars

I'm not allowed to leave comments , but it is possible to shorten the previous answer somewhat by not having Option Explicit. Taking advantage of some of the more dangerous features of VB6/VBA you can use the one below. No need to declare what the variable is and also the function doesn't need to be declared public either if going for ultimate shortness! Also the End If is not needed if it is on the same line.

Function P(N As Long)
    Dim I, O
    Do While N > 1: For I = 2 To N
    If N Mod I = 0 Then O = O & " " & I: N = N / I: Exit For: 
    Next: Loop: P = O
End Function

This can be tested by :

Public Sub TestP()
    Dim s: s = P(1806046)
    Debug.Print s
End Sub

Answer 5

74 75 Characters in Python

a=input();b=2
while b*b<=a:
    if a%b==0:print b;a/=b;b=1
    b+=1
print a

Derived from my TI-BASIC code for prime factorization.

Since I'm talking about TI-Basic...

77 Characters in TI-Basic

input a
2→b
while b²<a
a/b→c
if int(c)=c:then:disp b:c→a:1→b:end
b+1→b
end
disp a

Answer 6

C#, 366 characters

C# is not the most averbose language for something like this, but this is quite compact:

class P {
   static void Main(string[] a) {
      int i = int.Parse(a[0]);
      var p = new System.Collections.Generic.List<int>();
      for (int n = 2; i > 1; n++)
         if (p.Find(q => n % q == 0) == 0) {
            p.Add(n);
            while (i % n == 0) {
               System.Console.WriteLine(n);
               i /= n;
            }
         }
   }
}

Edit:
I saw that Noldorin used the List.Find method in his F# code, and realised that it would be a bit shorter than a foreach...

Edit:
Well, if it doesn't have to be a complete program...

C#, 181 characters

string f(int i) {
   var r = "";
   var p = new System.Collections.Generic.List<int>();
   for (int n = 2; i > 1; n++)
      if (p.Find(q => n % q == 0) == 0) {
         p.Add(n);
         while (i % n == 0) {
            r += "x" + n;
            i /= n;
         }
      }
   return r.Substring(1);
}

Compressed:

string f(int i){var r="";var p=new System.Collections.Generic.List<int>();for(int n=2;i>1;n++)if(p.Find(q=>n%q==0)==0){p.Add(n);while(i%n==0){r+="x"+n;i/=n;}}return r.Substring(1);}