Tree representation

Hi! I'm new to java and my boss wants me to represent n binary trees in one binary tree.
We have n binary trees, the root node of each tree has a name (identifying the tree) and a height, somehow he wants me to create some kind of super-tree of all this trees, and I really don't know what to do. As I understand he wants me to create one root node for this super-tree and set it's height to let's say a value like 2 times the highest tree we have , then the left child (T1) should be the tree with the highest value of height and the right child the second highest value (T2), then as T1's childs should be the following trees in height and so on..
Please could anyone give me any comments about this approach? Please let me know and accept my apologises if this post should be anywhere else, but I don't know where to post it

cristine,
<quoted-for-emphasis>
I don't follow you. Again: please explain the problem you're trying to solve.</quoted-for-emphasis>
That's about it... If you're asking us to help weigh up the pro's and con's of a full-sort-merge verses a list-of-list-of-trees then you're going to have to provender a hellofalot more information... basically you'll need to sit down and write a BRS, and an SRS, and precis your tech-arc... focusing on the tree datastructures in question of course... but yeah.... we need a lot more information in order to make any intelligent comments. There's a bit more to software engineering than "I prefer traffic lights to tomato sandwiches, but not when they are red".
What do you mean you don't know how to merge two trees?
Sounds like homework to me. Is it? Again no problem if it is... It just helps pitch the responses "at your level"... for instance I'll stop using mystery acronyms like SRS.
Cheers. Keith.

Similar Messages

Advanced:   How to traverse a tree representation in PL/SQL (procedure)?

I am looking to write a method that will create a collection of records, each of which represents a node in a tree.
TYPE t_all_folders IS TABLE OF get_all_folders%ROWTYPE INDEX BY PLS_INTEGER;
v_all_folders t_all_folders;
so first need help in figuring out what the cursor 'get_all_folders' would look like
I have a folder structure represented in a database that is used basically to show visually
(with a front end app) a folder structure (much like a folder structure in a file system).
So each row has an entry in the 'folders' table like do:
table folder:
     column           column
     folder_id          name
     1                    folder1               <= say this is a root folder
     2                    folder2               <= say this is a root folder
     3                    folder3               <= say this is a root folder
     4                    folder1a          <= all below are child folders..
     5                    folder1b
     6                    folder1c
     7                    folder1aa
     8                    folder1ab
     There is nothing in this table that indicates a hiearchy.
The hiearchy is represented by another single table with two columns
(I cannot change this, it is what it is)
There is no left node or right node (not like a tree), just imagine sub folders.
table: parent_child
     column          column
     parent_id     child_id
such that visually when the tables are queried and the UI uses a folder icon to
represent each row:
it would look like this:
     folder1                              1
          - folder1a                         2
               -folder1aa                    3
               - folder1ab                    4
          - folder1b                         5
               - folder1ba                    6
               - folder1bb                    7
          - folder1c                         8
     folder2                              9
     folder3                              10
I am attempting to create a query that will add to a collection folder records in the
order above (1..10)
In other words traverse the tree depth first going from:
          folder1 -> folder1a -> folder1aa -> folder1ab ->(back out to next level) folder1b -> folder1ba -> folder1bb -> folder1c
          then add folder2 (and traverse down that hiearch if needed)
          and then add folder3 to the colleciton and traverse down that hiearchy if there is one
          and continue adn so on.
          The requirement is to have them added to the collection in that order and when I iterate through the collection,
          they would of course need to be pulled out in that order (so use vararray with a counter to iterate through
          after the collection has been created.
After the collection has been created, I have to iterate in that specific order to create records in another table where there is a column that requires an integer value that is the 1... order they come out of the collection
and then have to iterate again and do something else in that order (and then other things - all the while needing in that order).
Edited by: user12200443 on Nov 19, 2012 11:49 AM

awesome, thanks for the help.
put this in 'schema.sql' and run to create a reference schema and data for the example
drop sequence seq_folders;
CREATE SEQUENCE seq_folders
INCREMENT BY 1
MINVALUE 1
START WITH 1
CACHE 1000;
drop table folders;
create table folders (
     folder_id number not null,
     name varchar2(20) not null
drop table parent_child;
create table parent_child (
     parent_id number not null,
     child_id number not null);
-- creation order (in order to have parent)
-- folder1
-- folder2
-- folder3
-- folder1a
-- folder1b
-- folder1c
-- folder1aa
-- folder1ab
-- folder1ac
-- folder1aaa
-- folder1aba
-- folder1aab
-- folder1abb
-- folder1aac
-- folder1abc
-- Visual hiearchy
-- folder1                              1
--      folder1a                         2
--           folder1aa               3
--                folder1aaa          4
--                folder1aab          5
--                folder1aac          6
--           folder1ab               7
--                folder1aba          8
--                folder1abb          9
--           folder1ac               10
--      folder1b                         11
--      folder1c                         12
-- folder2                              13
-- folder3                              14
--- insert folders
insert into folders(folder_id, name) values(seq_folders.nextval, 'folder1');
insert into folders(folder_id, name) values(seq_folders.nextval, 'folder2');
insert into folders(folder_id, name) values(seq_folders.nextval, 'folder3');
insert into folders(folder_id, name) values(seq_folders.nextval, 'folder1a');
insert into folders(folder_id, name) values(seq_folders.nextval, 'folder1b');
insert into folders(folder_id, name) values(seq_folders.nextval, 'folder1c');
insert into folders(folder_id, name) values(seq_folders.nextval, 'folder1aa');
insert into folders(folder_id, name) values(seq_folders.nextval, 'folder1ab');
insert into folders(folder_id, name) values(seq_folders.nextval, 'folder1ac');
insert into folders(folder_id, name) values(seq_folders.nextval, 'folder1aaa');
insert into folders(folder_id, name) values(seq_folders.nextval, 'folder1aba');
insert into folders(folder_id, name) values(seq_folders.nextval, 'folder1aab');
insert into folders(folder_id, name) values(seq_folders.nextval, 'folder1abb');
insert into folders(folder_id, name) values(seq_folders.nextval, 'folder1aac');
insert into folders(folder_id, name) values(seq_folders.nextval, 'folder1abc');
commit;
-- setup hiearchy
insert into parent_child(parent_id, child_id) values (0, (select folder_id from folders where name = 'folder1'));
insert into parent_child(parent_id, child_id) values (0, (select folder_id from folders where name = 'folder2'));
insert into parent_child(parent_id, child_id) values (0, (select folder_id from folders where name = 'folder3'));
-- 1a,1b,1c
insert into parent_child(parent_id, child_id) values ((select folder_id from folders where name ='folder1'), (select folder_id from folders where name = 'folder1a'));
insert into parent_child(parent_id, child_id) values ((select folder_id from folders where name ='folder1'), (select folder_id from folders where name = 'folder1b'));
insert into parent_child(parent_id, child_id) values ((select folder_id from folders where name ='folder1'), (select folder_id from folders where name = 'folder1c'));
-- aa,ab,ac
insert into parent_child(parent_id, child_id) values ((select folder_id from folders where name ='folder1a'), (select folder_id from folders where name = 'folder1aa'));
insert into parent_child(parent_id, child_id) values ((select folder_id from folders where name ='folder1a'), (select folder_id from folders where name = 'folder1ab'));
insert into parent_child(parent_id, child_id) values ((select folder_id from folders where name ='folder1a'), (select folder_id from folders where name = 'folder1ac'));
-- aaa,aba,aab
insert into parent_child(parent_id, child_id) values ((select folder_id from folders where name ='folder1aa'), (select folder_id from folders where name = 'folder1aaa'));
insert into parent_child(parent_id, child_id) values ((select folder_id from folders where name ='folder1aa'), (select folder_id from folders where name = 'folder1aab'));
insert into parent_child(parent_id, child_id) values ((select folder_id from folders where name ='folder1aa'), (select folder_id from folders where name = 'folder1aac'));
-- aba,abb,abc
insert into parent_child(parent_id, child_id) values ((select folder_id from folders where name ='folder1ab'), (select folder_id from folders where name = 'folder1aba'));
insert into parent_child(parent_id, child_id) values ((select folder_id from folders where name ='folder1ab'), (select folder_id from folders where name = 'folder1abb'));
insert into parent_child(parent_id, child_id) values ((select folder_id from folders where name ='folder1ab'), (select folder_id from folders where name = 'folder1abc'));
commit;
then run this to get the error message
WITH joined_data     AS
     SELECT     f.folder_id,     f.name,     pc.parent_id
     FROM     folders     f
     JOIN     parent_child     pc ON pc.child_id = f.folder_id
SELECT     j.*,     ROWNUM
AS r_num
FROM joined_data     j
START WITH     parent_id =0
CONNECT BY     parent_id= PRIOR child_id
ORDER SIBLINGS BY     name;
thanks for the help, hopefully I can find a way to read the rows/record into a data structure (does not have to be a single sql statement - can be anything I can do in PL/SQL.
Edited by: user12200443 on Nov 19, 2012 5:55 PM

Tree representation of objects

Hello
I need to return back a collection of objects from the database to my jsp, to be represented in a tree structure. I need to represent my objects in a tree structure so that it can be passed back from my server to the client.
Any idea how to represent this? I thought of using LinkedList, but I understand that it cannot be used since a node in the tree can have many childs directly under it.
I am thinking of representing this using a TreeMap, but not sure whether it is the best approach. Can you please help me out?
Best Regards
peduser

peduser wrote:
Any idea how to represent this? I thought of using LinkedList, but I understand that it cannot be used since a node in the tree can have many childs directly under it.Why is that a problem?
I am thinking of representing this using a TreeMap, but not sure whether it is the best approach. Can you please help me out?What happened when you tried it that way? Did you experience any problems?
See the API for TreeMap and TreeSet, try one out, and see if you experience any problems.
Link to the API because the link tag seems to be horribly broken: http://download-llnw.oracle.com/javase/6/docs/api/

Duplicate nodes in ADF Tree

Duplicate Entries in ADF Tree
Hi,
Iam facing issue with ADF Tree representation. Getting content from DB. I've a table with self reference. Iam able to provide check box for each node. Following is the usecase of issue
a->b->c->1.xml
a->b1->c1->2.xml
a->b2->c2->3.xml
Issue 1: It's dispaling 3 a's at the first level. But it should display a once within that b,b1,b2 as sub levels.
Even though it's showing 'a' three times, if we click on second & third 'a', first 'a' is effecting. Please suggest to filter duplicate entries while displaing. Following is code snippet of jspx.
<af:tree value="#{bindings.ParentMDTopic1.treeModel}" var="node"
selectionListener="#{bindings.ParentMDTopic1.treeModel.makeCurrent}"
rowSelection="multiple" id="t1"
partialTriggers="#{pageFlowScope.mBean.checkboxFlag.addValueChangeListener}">
<f:facet name="nodeStamp">
<af:group id="g1">

<af:selectBooleanCheckbox label="Label 1" id="sbc2"
value="#{node.checkboxFlag}"
autoSubmit="true"
valueChangeListener="#{pageFlowScope.mBean.checkBoxChange}"/>
<af:outputText value="#{node}" id="ot1"/>
</af:group>
</f:facet>
</af:tree>
Issue 2: Select/Deselect functionality. If we click on any node, the child nodes & sub levels till leaf nodes should be in select state. Similarly for deselect functionality.
In order to acheve functionality, Created two transient attributes of boolean & string type. I tired to debug the ManagedBean, seems to be it's traversing to sublevels & changing the transient attribute. But while display it's not effeting. Please suggest a hint on this. It could be great if you provide some useful pointers to refer.
Thanks in advance,
Samba.

Hi,
I've provided Parent-Child relationship(Self-reference).
Following is the table structure with primary/foreign key constraints.
DELIVERY_VERSION_ID (PK)(FK)
HIERARCHY_ID (PK)(FK)
DOC_GUID (PK)
PARENT (FK)
CURRENTTITLE
LANGUAGE
Please let me know, if you have any comments on table structure.
Following is the sample data in table
DELIVERY_VERSION_ID     DOC_GUID Parent HIERARCHY_ID
3               a     null     a_b_c
3               b     a     a_b_c
3               c     b     a_b_c
3               1.xml     c     a_b_c
3               a     null     a_b1_c1
3               b1     a     a_b1_c1
3               c1     b1     a_b1_c1
3               2.xml     c1     a_b1_c1
3               a     null     a_b2_c2
3               b2     a     a_b2_c2
3               c2     b2     a_b2_c2
3               3.xml     c2     a_b2_c2
Thanks,
Samba.

Tree component customization

Hi all,
I'm new to flex and having a hard time figuring out the best way to approach the following problem (in Flex context, _not_ AIR):
I need a tree representation of some hierarchical/composite data structures as depicted below (for those familiar with XMLSpy, the diagram is similar to the XSD tree structure diagrams):                                                                                     |-------------|
                                                                                     | Child       |
                                                                                     | child info |
                                      |------------------|                           |-------------|
                                   |--| Child            |--------- Choice (x) ------|
                                   | | Child Info      (x)                          |-------------|
                                   | --------------------                           | Child       |
                                   |                                                 | child info |
---------------                    | |------------------|                           |-------------|
| Parent      |------ Sequence (x)-|--| Child            |
| Parent Info (x)                  |   | Child Info     (x)
---------------                    |   --------------------
                                   |
                                   | |------------------|
                                   |--| Child            |
                                      | Child Info      (x)
The (x) in the picture are the collapse/expand buttons.
What would be the best way to approach this project ?
- Is it a customization of the standard Tree component + custom Tree Item Renderer ?
- The nodes should be expandable/collapsible + selectable (additional information to be displayed on selection of node without expand/collapse effect)
- For the nodes would it make sense to derive them from the ToggleButton ? (and what would be the most sensefull way of introducing the second line on the button ? Or just building a proper graphical component for it (derived from Group)?
- What is the most effective way to deal with the balancing of the tree in such a way that subtrees move out of the way/in place on expand resp. collapse of nodes ? (through (H/V)groups ?)
- What would be the most efficient way to deal with the connectors between nodes ?
- dataprovider would be an XML structure - what is the best place to put the building algo ? (Every node know how to create itself and the first level children ? Or a tree traverse on the XML structure, building all components in one go ?)
Any advice/thoughts/references are welcome !
Thanks in advance,
Best regards,
Bart

Sorry for the "text picture" - if you copy/paste it in word (with courier new font
), the picture becomes clear ;-)

Bette way to referenced tree model nodes from UI to perform actions on them

A singleton facade is built.
Its init() method loads several "tree model configs", each of them referenced by a name.
This singleton creates a Project instance for a given "tree model config" calling the facade method -> createProject(String pjrName, String modelConfigName)
When the Project is built a new Model instance is set ( remember the model instance is a tree holding nodes )
The new Project instance built is added to a List that the facade has and then it's returned to the UI part that called ->createProject(prjName,modelconfigName)
Given the Project instance the UI has to build a JTree representation of the model that the project references and the UI will have button actions that should call methods of the Nodes of the model referenced by the Project.
Doing it this way the UI will be able to reference objects directly without going through the facade.
Maybe I should return to the UI something like a ProjectKey instance instead of letting have the UI the Project instance ?
It should be better if I process the possible node actions behind the Facade and not the UI, but how can I do it ?
Having a ProjectKey in my UI I could ask the facade a model tree representation but not having the real nodes, otherwise having some NodeKey instances ?

Sounds like you want to represent a tree structure, without a reference to the real tree.
I'll take it further: maybe you don't want the UI to know there's a real tree data-structure with nodes and pointers to children, because maybe you build the tree on the fly from a database.
So use the Builder pattern instead of committing to a specific data structure.
Google results for Builder pattern: http://www.google.com/search?hl=en&q=builder+pattern&btnG=Google+Search
Your UI should know how to construct nodes and children graphically, when told. This means it should have methods like addNode, but related to the domain: addSubProject maybe.
A Project object is the Director, knowing which part goes where, but it doesn't know the real end result (a JPanel or HTML). So it has a method buildProject(Builder e) or exportProject(Exporter e), where all logic of assembling the parts is.
When you have that, write a class JTreeProjectExporter implements Exporter.
Hope this helps.

How to drag and drop nodes in Tree?

Hi,
I want to drag and drop nodes in the tree. For example a tree represents the hierarchy of employees reporting in an organization by using tree.I want to change the reporting an employee visible in the tree by simple drag and drop operation in place of going to another form for updating each employee record indiviually.
Regards
Piyush

Ron,
I looked into implementing drag / drop in one of the apex trees I created today and ran across this thread. Thank you Ron for the links, it helped a lot.
I added the code below to my page's "Execute when Page Loads" (tree region id is "tree_reg") and the tree is now drag/drop enabled.
It did break the [+] icon from collapsing the tree though ... but the apex.widget.tree buttons still work
var regTree = apex.jQuery("#tree_reg").find("div.tree");
regTree.tree({
callback : {
onmove: function(NODE, TREE_OBJ, REF_NODE, TYPE)
{alert(NODE.id+" "+TREE_OBJ.id+" "+ REF_NODE);}
});Next, I plan on creating a AJAX call using NODE.id, TREE_OBJ.id, and REF_NODE
V/R
Ricker

Mx:tree not updating dynamically

Hi
I am trying to simulate a directory structure through a tree
representation. I use a cfdirectory call through a RemoteObject and
attach the result to an XML object which then becomes the tree
dataprovider. The first time the tree opens fine with all directory
nodes. Each time I chose a directory to fetch the underlying
subfolders the tree component becomes messy as if the tree does not
refresh dynamically.
I am doing something wrong. Any ideas would be very welcome.
var mytree_struct:XML;
private function buildtree ():void {
for (var i:int = 0; i < aResult.length; i++) {
var newnode:XML = new XML();
newnode = <directory label={aResult.getItemAt(i).Name}
isBranch="true"> </directory>;
mytree_struct=mytree_struct.appendChild(newnode);
My tree event handler which should add new nodes (
subfolders) of the selected folder. For the moment I am just trying
it out with a test variable k.toString().
public function treeChanged(event:Event):void {
for (var k:int =0; k <10;k++ ) {
var newnode:XML = new XML();
var temp1:String = k.toString();
newnode = <subdirectory label= {temp1}
isBranch="true"> </subdirectory>;
event.currentTarget.selectedItem.appendChild(newnode);
}

in italian
http://www.augitaly.com/flexgala/index.php?cmd=newsreader&id=129
http://www.augitaly.com/flexgala/index.php?cmd=newsreader&id=123

Synching ADF tree table and adf tree

Hi,
I am facing issue in syncing the data between adf treetable and tree
Here is my use case
I have one treetable and one tree in the UI..
treeTable shows the hierarchical view and tree represents the flat view of the same data.
If I delete the data in the tree view and then go to treeTable the deleted shows still show in this view and same happens in other case...
Any pointer to this will be of great help
Thanks

Do you see that you are using difference object in below table gui def.
snapshotList and snapshotList1.
ADF code:
<af:table value="#{bindings.snapshotList1.collectionModel}"
var="row" rows="#{bindings.snapshotList1.rangeSize}"
emptyText="#{bindings.snapshotList1.viewable ? 'No data to display.' : 'Access Denied.'}"
fetchSize="#{bindings.snapshotList1.rangeSize}"
width="53.5%" rowBandingInterval="0" id="t1"
selectionListener="#{bindings.snapshotList.collectionModel.makeCurrent}"
selectedRowKeys="#{bindings.snapshotList.collectionModel.selectedRow}"
rowSelection="single"
visible="#{viewScope.myBean.isFlat}"
binding="#{viewScope.myBean.table}">
Please generate getter and setter both.
MB code..
private RichTable table;
public RichTable getTable() {
return table;
public void setTreeTable(RichTreeTable treeTable) {
this.treeTable = treeTable;
delete button is outside.. it is in a panelGroupLayout
<af:commandButton text="#{vtsnapshotuiBundle.DELETE}"
id="delete_id"
disabled="#{viewScope.myBean.buttonDisable}"
actionListener="#{my_delete_func}"
Thanks,
Hasim

What does it mean when the usecounts of Parse Tree for a view is incrementing when a select query is issued against the view?

I'm using SQL Server 2008 R2 (10.50.4033) and I'm troubleshooting an issue that a select query against a specific view is taking more than 30 seconds consistently.   The issue just starts happening this week and there is no mass changes in data.
The problem only occur if the query is issued from an IIS application but not from SSMS. One thing I noticed is that sys.dm_exec_cached_plans is returning 2 Parse Tree rows for the view - one created when the select query is issued
1st time from the IIS application and another one created when the same select query is issued 1st time from SSMS.   The usecounts of the Parse Tree row for the view (the IIS one) is increasing whenever the select query is issued.  The
usecounts of the Parse Tree row for the view (the SSMS one) does not increase when the select query is issued again.
There seems to be a correlation between the slowness of the query and the increasing of the usecounts of the Parse Tree row for the view.
I don't know why there is 2 Parse Tree rows for the view. There is also 2 Compiled Plan rows for the select query.
What does the Parse Tree row mean especially the usecounts column?

>> The issue just starts happening this week and there is no mass changes in data.
There might be a mass changes in the execution plan for several reason without mass changes in data
If you have the old version and a way to check the old execution plan, and compare to the new one, that this should be your starting point. In most cases you don't have this option and we need to monitor from scratch.
>> The problem only occur if the query is issued from an IIS application but not from SSMS.
This mean that we know exactly what is the different and you can compare both execution plan. once you do it, you will find that they are no the same. But this is very common issue and we can know that it is a result of different SETting while connecting
from different application. SSMS is an external app like any app that you develop in Visual studio but the SSMS dose not use the Dot.Net default options.
Please check this link, to find the full explanation and solutions:
http://www.sommarskog.se/query-plan-mysteries.html
Take a look at sys.dm_exec_sessions for your ASP.Net application and for your SSMS session.
If you need more specific help, then we need more information and less stories :-)
We need to see the DDL+DML+Query and both execution plans
>> What does the Parse Tree row mean
I am not sure what you mean but the parse tree represents the logical steps necessary to execute the query that has been requested. you can check this tutorial about the execution plan: https://www.simple-talk.com/sql/performance/execution-plan-basics/ or
this one: http://www.developer.com/db/understanding-a-sql-server-query-execution-plan.html
>> regarding the usecount column or any other column check this link:
https://msdn.microsoft.com/en-us/library/ms187404.aspx?f=255&MSPPError=-2147217396.
Ronen Ariely
[Personal Site]    [Blog]    [Facebook]

Create family tree

hello,
i want to create a visual family tree so i looked for softwares that do that and found that there is no software that i can use with htmldb.
does anybody know how can i do that in htmldb ?
does anybody know of a good and simple software that will export the family tree so i can import it easily to htmldb ?
thanks

1) Data File Format
One possible format is GEDCOM. (GEDCOM stands for Genealogical Data COMmunications. http://www.math.clemson.edu/~rsimms/genealogy/ll/gedcom55.pdf ) Most if not all Genealogy software can generate that file format.
A new format is GedML. It combines the format a GEDCOM with XML. At this point in time it is not as widely supported as GEDCOM is.
2) Database Tables
You should model the data such that you have a PERSON table and a FAMILY table with foreign keys from FAMILY to PERSON.
3) Load Data File
Write a procedure to process the data file from #1 and populate the tables in #2.
4) Family Tree Representation
Create a Navigational Shared Component of type tree to display the family tree.

Problem with display of files in remote server

hi,
i am trying to display to the files on a remote server using JTree. i am able to display local files and directories using JTree but i don't know how to display remote files. can anyone explain how to do it?
Thank you,
npaila

hi,
i have exactly the same problem.
Each node of the tree represents a directory. it can be a local or a remote one.
The only difference is the definition of the File class; the TreeNode class is the same for both.
Everything works correctly with local Files and fails with remote files.
Everything means : directory creation, supression, rename, expand all recursive subdirectories.
I can expand each node, even the ones associated with remote files, with user actions (mouse click, key typed) but I can't expand any node by programing.
Each action is efficient on the remote server, but the display doesn't change at all.
Something strange is that when I create a new JTree with a remote file as the root, expand all its recursive subdirectories and then display the Tree, it has correctly expanded.
Is it a refresh problem ?
Please help us, give us a clue...
Thx for advance
chocodup

I need a solution of this complicated problem to finalize my final project

Introduction
This project revolves around an important text processing task, text compression. In particular, you will be required to encode a sequence of words read from a source file into binary strings (using only the characters 0 and 1). It is important to note that text compression makes it possible to minimize the time needed to transmit text over a low-bandwidth channel, such as infrared connection. Moreover, text compression is helpful in storing large documents more efficiently. The coding scheme explored in this project is the Huffman Coding Scheme. While standard encoding schemes, such as Unicode and ASCII, use fixed-length binary strings to encode characters, Huffman coding assigns variable-length codes to characters. The length of a Huffman code depends on the relative frequency of its associated character. Specifically, Huffman coding capitalizes on the fact that some characters are used more frequently than others to use short codewords when encoding high-frequency characters and long codewords to encode low-frequency characters. Huffman coding saves space over state of the art fixed-length encoding and is therefore at the heart of file compression techniques in common use today. Figure 1 shows the relative frequencies of the letters of the alphabet as they appear in a representative sample of English documents.
Letter     Frequency     Letter     Frequency
A     77     N     67
B     17     O     67
C     32     P     20
D     42     Q     5
E     120     R     59
F     24     S     67
G     17     T     85
H     50     U     37
I     76     V     12
J     4     W     22
K     7     X     4
L     42     Y     22
M     24     Z     2
Figure 1. Relative frequencies for the 26 letters of the alphabet.
Huffman coding and decoding
Huffman’s algorithm for producing optimal variable-length codes is based on the construction of a binary tree T that represents the code. In other words, the Huffman code for each character is derived from a full binary tree known as the Huffman coding tree, or simply the Huffman tree. Each edge in the Huffman tree represents a bit in a codeword, with each edge connecting a node with its left child representing a “0” and each edge connecting a node with its right child representing a “1”. Each external node in the tree is associated with a specific character, and the Huffman code for a character is defined by the sequence of bits in the path from the root to the leaf corresponding to that character. Given codes for the characters, it is a simple matter to use these codes to encode a text message. You will have simply to replace each letter in the string with its binary code (a lookup table can be used for this purpose).
In this project, you are not going to use the table given in Figure 1 to determine the frequency of occurrence per character. Instead, you will derive the frequency corresponding to a character by counting the number of times that character appears in an input file. For example, if the input file contains the following line of text “a fast runner need never be afraid of the dark”, then the frequencies listed in the table given in Figure 2 should be used per character:
Character          a     b     d     e     f     H     i     k     n     O     r     s     t     u     v
Frequency     9     5     1     3     7     3     1     1     1     4     1     5     1     2     1     1
Figure 2. The frequency of each character of the String X.
Based on the frequencies shown in Figure 2, the Huffman tree depicted in Figure 3 can be constructed:
Figure 3. Huffman tree for String X.
The code for a character is thus obtained by tracing the path from the root of the Huffman tree to the external node where that character is stored, and associating a left edge with 0 and a right edge with 1. In the context of the considered example for instance, the code for “a” is 010, and the code for “f” is 1100.
Once the Huffman tree is constructed and the message obtained from the input file has been encoded, decoding the message is done by looking at the bits in the coded string from left to right until all characters are decoded. This can be done by using the Huffman tree in a reverse process from that used to generate the codes. Decoding the bit string begins at the root of the tree. Branches are taken depending on the bit value – left for ‘0’ and right for ‘1’ – until reaching a leaf node. This leaf contains the first character in the message. The next bit in the code is then processed from the root again to start the next character. The process is repeated until all the remaining characters are decoded. For example, to decode the string “0101100” in the case of the example under study, you begin at the root of the tree and take a left branch for the first bit which is ‘0’. Since the next bit is a ‘1’, you take a right branch. Then, you take a left branch (for the third bit ‘1’), arriving at the leaf node corresponding to the letter a. Thus, the first letter of the coded word is a. You then begin again at the root of the tree to process the fourth bit, which is a ‘1’. Taking 2 right branches then two left branches, you reach the leaf node corresponding to the letter f.
Problem statement
You are required to implement the Huffman coding/decoding algorithms. After you complete the implementation of the coding/decoding processes, you are asked to use the resulting Java code to:
1.     Read through a source file called “in1.dat” that contains the following paragraph:
“the Huffman coding algorithm views each of the d distinct characters of the string X as being in separate Huffman trees initially with each tree composed of a single leaf node these separate trees will eventually be joined into a single Huffman tree in each round the algorithm takes the two binary trees with the smallest frequencies and merges them into a single binary tree it repeats this process until only one tree is left.”
2.     Determine the actual frequencies for all the letters in the file.
3.     Use the frequencies from the previous step to create a Huffman coding tree before you assign codes to individual letters. Use the LinkedBinaryTree class that we developed in class to realize your Huffman coding trees.
4.     Produce an encoded version of the input file “in1.dat” and then store it in an output file called “out.dat”.
5.     Finally, the decoding algorithm will come into play to decipher the codes contained in “out.dat”. The resulting decoded message should be written to an output file called “in2.dat”. If nothing goes wrong, the text stored in “in1.dat” and the one in “in2.dat” must match up correctly.

jschell wrote:
I need a solution of this complicated problem to finalize my final project The solution:
1. Write code
2. Test code3. If test fails, debug code, then go to step 2.

Possible to overwrite parse method in DOM with SAX Handler?

Hi,
Is it possible to overwrite the parse method within DOM?
What a want to do is:
     private Node parseXml( String text ) throws SAXParseException, SAXException, IOException, ParserConfigurationException
          SAXParserFactory factory = SAXParserFactory.newInstance();
               factory.setNamespaceAware(true);
               SAXParser parser = factory.newSAXParser();
               TestHandler handler = new TestHandler();
               // Parse the file
               parser.parse(new InputSource(new StringReader(text)), handler);
          return (Node)handler.getRoot();
     } //end parseXml()The reason I want to use this is that within SAX I can write my own line counter so I keep a count of which node is on which line of text.
What I was thinking is that I could use SAX to return DOM Nodes with the line number attached, possibly using the node.setUserData() method?!
I have tried to play around with it and it doen't seem to work, can anyone help?
Cheers Alex

I have managaed to re-write my SAX parser to create a JTree, this works perfectly I can move through the tree and each line of text that corresponds to the node is highlighted.
My problem is however that in my application I have used the DOM structure throughout so some of the functionality is lost.
Is I understand that JAXP uses both SAX and DOM together, so I was wondering if it is possible to combine my sax parse method within the DOM?
If anything is unclear please say and I will try and explain better. The main reason for doing this is that I want to keep a reference to which line of text each node of the dom tree represents. I have not been able to implemnet one in DOM however using SAX I have managed.
Many thanks,
Alex

Forte 6U2 - poor performance of std::map::operator[]

I discovered to my horror this morning that Forte 6U2 implementation of std::map (at least at the patch level I'm working with) ALWAYS default constructs a value_type when operator[] is invoked - even if value_type already exists in the map.
Any reasonable STL implementation first uses lower bound to search, and failing to find an appropriate element, uses the resulting iterator as an insertion hint, only then default constructing a value_type (and therefore a mapped_type) element.
The existing implementation in Forte 6U2 imposes an absurd penalty on the use of the subscript operator when mapped_type's default construction semantics are non-trivial. While "correct" in the sense that the contract for std::map::operator[] is met, I cannot imagine that this was an intentional design choice given the performance implications. How can I get this issue addressed?

Well, I wasn't making any claim about the efficiency of the underlying tree representation - only the fact that operator[] unconditionally default constructs a mapped_type object, even if there is already an appropriate element in the map, which is no good at all. I'll try your request for enhancement thing though...
While I would very much like to switch to using STLport vs. the RW stl, a compiler upgrade is not the answer here.

Tree representation

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