Data structure

Ruby
1

Hello All,

I would like to implement a tree with the following properties.

  1. The tree is balanced.
  2. Each node has a max of 5 sub nodes and min of ceil(5/2) sub nodes.
  3. The tree remains static. Number of nodes known from the beginning.

How would I implement this in ruby?

Thanks,
Vandana.

2

Vandana wrote:

Hello All,

I would like to implement a tree with the following properties.

  1. The tree is balanced.
  2. Each node has a max of 5 sub nodes and min of ceil(5/2) sub nodes.
  3. The tree remains static. Number of nodes known from the beginning.

How would I implement this in ruby?

Thanks,
Vandana.

If the number of nodes are known, then an array based implementation
would be better. So basically, arr[0] is the root. Since it has maximum
5 sub nodes, index 1-5 are the roots children, 6-10 are array[1]'s
children and so on. The function to find node x’s (five) children then
would be x5 + 1, x5 + 2, …, x*5 + 5. Similarly, floor((x - 1) /5)
will be the parent’s node.

Do check the function coz I made them as I typed.

3

On 2008-06-29, Vandana [email protected] wrote:

  1. The tree is balanced.
  2. Each node has a max of 5 sub nodes and min of ceil(5/2) sub nodes.
  3. The tree remains static. Number of nodes known from the beginning.

How would I implement this in ruby?

I would suggest the use of an algorithm.

4

2008/6/30 Shashank A. [email protected]:

If the number of nodes are known, then an array based implementation
would be better. So basically, arr[0] is the root. Since it has maximum
5 sub nodes, index 1-5 are the roots children, 6-10 are array[1]'s
children and so on. The function to find node x’s (five) children then
would be x5 + 1, x5 + 2, …, x*5 + 5. Similarly, floor((x - 1) /5)
will be the parent’s node.

This might not even be needed depending on the usage of the tree, i.e.
if the tree is ordered then a binary search on the array might be
sufficient.

Btw, RAA also references a read black tree implementation…

Kind regards

robert

5

On Jun 30, 7:01 am, Robert K. [email protected] wrote:

  1. Each node has a max of 5 sub nodes and min of ceil(5/2) sub nodes.

–
use.inject do |as, often| as.you_can - without end

Thanks for your replies. My problem is i dont know how to keep the
tree balanced.

For example if there are a total of 17 nodes, then I need 1 main_root
node, and I could use 3 sub_root_nodes, with the first 2 having 5
children and the last one having just 2 children. This situation I
want to avoid. More ideally all the sub nodes should have number of
children ranging from 3 -5
I dont want some of the sub_nodes to be full and the last one to be
not even half full.

Any ideas on how to do this best?

6

-------- Original-Nachricht --------

Datum: Mon, 30 Jun 2008 22:22:18 +0900
Von: Vandana [email protected]
An: [email protected]
Betreff: Re: data structure

  1. The tree is balanced.
    would be x5 + 1, x5 + 2, …, x*5 + 5. Similarly, floor((x - 1) /5)
    robert
    want to avoid. More ideally all the sub nodes should have number of
    children ranging from 3 -5
    I dont want some of the sub_nodes to be full and the last one to be
    not even half full.

Any ideas on how to do this best?

Vandana,

have a look here:

http://www.rubyquiz.com/quiz137.html

Best regards,

Axel

7

Am I right that given a number of nodes N, you want to know how to
construct a most balanced tree? You’re not so interested in dynamic
behaviour - you just want the best static tree to keep it as balanced as
possible?

This is more of a maths question than a datastructures question. I think
you’d want to give a stronger definition of what you want from the tree.
For example, I’d imagine that you’d want only the direct leaf’s parents
to
not be full, and all other nodes to have 5 children?

Cheers,
B

8

2008/6/30 Vandana [email protected]:

  1. The tree is balanced.
    will be the parent’s node.

children ranging from 3 -5
I dont want some of the sub_nodes to be full and the last one to be
not even half full.

Any ideas on how to do this best?

Not sure what you are after. If you need a balanced tree you can just
use the red black tree from RAA. And, as I said, hiding a sorted
Array in some class with a tree like API might be sufficient if this
is a particular use case.

If you want to implement this yourself there are explanations in about
every textbook about balanced trees. This is pretty basic stuff and
there’s even documentation online, e.g.
Red–black tree - Wikipedia - if this is homework I
strongly suggest to read about tree balancing and implementing this
yourself vs. trying to extract an implementation from a public
community.

Cheers

robert

9

On Jun 30, 10:05 am, Robert K. [email protected] wrote:

I would like to implement a tree with the following properties.
children and so on. The function to find node x’s (five) children then

children and the last one having just 2 children. This situation I
is a particular use case.
robert

–
use.inject do |as, often| as.you_can - without end

Thanks all.

From my understanding Red-Black trees are solely used for bianry
trees.
I doubt I can use it for this purpose.

Consider the following scenario: I have 16 nodes and I want to create
a balanced tree such that each sub_node has a max of 7 nodes.
(example)
I can create the tree in the following 2 ways:

Case 1: Make a root node, with 3 sub_nodes, 2 sub_nodes have 7 leaf
nodes and the third sub_node of the root node has 2 leaf nodes.

Case 2: Make a root node, with 3 sub_nodes, distribute the leaf nodes
such that all 3 sub_nodes have 5 leaf nodes and 1 of them has an
extra.

I am interested in case 2.

Regarding the dynamic behavior: I must first construct this and then
be able to move around the leaf nodes and ensure that this ‘balance’
is not lost.
I know I have to use AVL principles of rotation, but since text books
explain only for binary trees, i wanted some help on it.
Any ideas/pointers to the correct group to post this will be most
helpful.

@Robert: No this is not homework question :slight_smile:

Thanks
Vandana