Can anyone help me with partition numbers?

[whoals]

A partition of a positive integer n is a representation of n as the sum of any number of positive integral parts. For example, there are 7 partitions of the number 5: 1+1+1+1+1, 1+1+1+2, 1+1+3, 1+2+2, 1+4, 2+3 and 5. Define a function parts which returns the list of distinct partitions of an integer n. For example, parts 4 = [[1,1,1,1],[1,1,2],[1,3],[2,2],[4]].

[jerzy.karczmarczuk]

whoals (sent by Nabble.com):

> Define a function parts which returns the list of distinct partitions of an
> integer n.

Send this query perhaps to haskell-homeworks  list?

JK


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[Cale Gibbard]

First of all, read this :)
http://haskell.org/hawiki/HomeworkHelp

There doesn't appear to be a list for Haskell homework help in the
list of mailing lists on haskell.org. If Jerzy knows more about one,
he might be able to provide some information there.

We'll be happy to help, but what have you already tried? This looks
just exactly like the problem text.

 - Cale

On 24/11/05, whoals (sent by Nabble.com) <lists@...> wrote:

>  A partition of a positive integer n is a representation of n as the sum of
> any number of positive integral parts. For example, there are 7 partitions
> of the number 5: 1+1+1+1+1, 1+1+1+2, 1+1+3, 1+2+2, 1+4, 2+3 and 5. Define a
> function parts which returns the list of distinct partitions of an integer
> n. For example, parts 4 =
> [[1,1,1,1],[1,1,2],[1,3],[2,2],[4]].
> ________________________________
>  Sent from the Haskell - Haskell-Cafe forum at Nabble.com.
> _______________________________________________
> Haskell-Cafe mailing list
> Haskell-Cafe@...
> http://www.haskell.org/mailman/listinfo/haskell-cafe
>
>
>

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[Fan Wu]

partition n = part n $ map (:[]) [1..n]
              where
                  part n [] = []
                  part n (x:xs)
                    |  s == n    = x: r
                    |  s > n     = r
                    |  otherwise = foldr (:) (part n $ map (:x) [h..n-1]) r
                    where
                       h = head x
                       s = sum x
                       r = part n xs


Main> partition 4
[[4],[2,2],[3,1],[2,1,1],[1,1,1,1]]   -- I guess the order doesn't matter here.


I myself is a newbie to Haskell. Every time I finished some code like
this I was amazed at the elegance and expressiveness of the language.
It's simply a different experience which you can't get from C/C++.

I hope you have spent enough time on it before you look at this,
otherwise you just missed some fun Haskell/homework/life has offered
you:-)

Cheers,
Fan


On 11/24/05, whoals (sent by Nabble.com) <lists@...> wrote:

>  A partition of a positive integer n is a representation of n as the sum of
> any number of positive integral parts. For example, there are 7 partitions
> of the number 5: 1+1+1+1+1, 1+1+1+2, 1+1+3, 1+2+2, 1+4, 2+3 and 5. Define a
> function parts which returns the list of distinct partitions of an integer
> n. For example, parts 4 =
> [[1,1,1,1],[1,1,2],[1,3],[2,2],[4]].
> ________________________________
>  Sent from the Haskell - Haskell-Cafe forum at Nabble.com.
> _______________________________________________
> Haskell-Cafe mailing list
> Haskell-Cafe@...
> http://www.haskell.org/mailman/listinfo/haskell-cafe
>
>
>

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