Rerooting can be done differently in hierarchical tree
representation: instead of pairs it has one list of
parent indices.
I wonder if verb "reroot" below can be represented
using C. cycles?
|: t3=: 0 1,0 2,1 3,1 4,i.0 2
0 0 1 1
1 2 3 4
>tree t3
+- 3
+- 1 -+- 4
- 0 -+- 2
rep1 t3 NB. hierarchical representation, root is _1
_1 0 0 1 1
4 rootpath~ rep1 t3 NB. path from 4 to root
4 1 0
To reroot into node 4, apply
4 (rootpath~ reroot ]) rep1 t3
1 4 0 1 _1
>tree rep2 4 (rootpath~ reroot ]) rep1 t3
+- 0 --- 2
- 4 --- 1 -+- 3
Here's collected defs
rep1=: ((_1,[) /: [EMAIL PROTECTED],])/@|: NB. hier-index repr. (1 row)
rep2=: (#~ 0<:{."1)@(,. [EMAIL PROTECTED]) NB. back to 2 column pairs
rootpath=: ({~ [^:(0<:[) ])^:a: NB. path to root in rep1
reroot=: (_1|.!._1])@[`[`] } NB. flip path in rep1
--- On Mon, 5/19/08, Oleg Kobchenko <[EMAIL PROTECTED]> wrote:
> Looks like you just need to
> flip each pair in path from old root to new root
>
> |: t1 (|."[EMAIL PROTECTED])}~ c i. }: (p {~ c i. ])^:(c e.~])^:a: 3
> 1 0 3 2 2 3 3 4 4 4 4 5 5 6 6 6 6 7 7
> 0 2 1 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
> tree t1 (|."[EMAIL PROTECTED])}~ c i. }: (p {~ c i. ])^:(c e.~])^:a: 3
> +----------------------------------+
> | +- 8 |
> | +- 9 |
> | +- 4 -+- 10|
> | | +- 11|
> | +- 1 --- 0 --- 2 -+ +- 12|
> | | +- 5 -+- 13|
> | | +- 14 |
> | | +- 15 |
> |- 3 -+- 6 -+- 16 |
> | | +- 17 |
> | | +- 18 |
> | +- 7 -+- 19 |
> +----------------------------------+
>
>
> --- On Mon, 5/19/08, Jose Mario Quintana <[EMAIL PROTECTED]> wrote:
>
> > A directed tree can be rerooted at any of its nodes. For
> > example, t1 from
> > http://www.jsoftware.com/jwiki/Essays/Tree_Display ,
> >
> >
> > |:t1
> > 0 0 1 2 2 3 3 4 4 4 4 5 5 6 6 6 6 7 7
> > 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
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