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  • Why create a Huffman tree per character instead of a Node?

    - by Omega
    For a school assignment we're supposed to make a Java implementation of a compressor/decompresser using Huffman's algorithm. I've been reading a bit about it, specially this C++ tutorial: http://www.cprogramming.com/tutorial/computersciencetheory/huffman.html In my program, I've been thinking about having Nodes that have the following properties: Total Frequency Character (if a leaf) Right child (if any) Left child (if any) Parent (if any) So when building the Huffman tree, it is just a matter of linking a node to others, etc. However, I'm a bit confused with the following quote (emphasis mine): First, every letter starts off as part of its own tree and the trees are ordered by the frequency of the letters in the original string. Then the two least-frequently used letters are combined into a single tree, and the frequency of that tree is set to be the combined frequency of the two trees that it links together. My question: why should I create a tree per letter, instead of just a node per letter and then do the linking later? I have not begun coding, I'm just studying the algorithm first, so I guess I'm missing an important detail. What is it?

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  • Why don't we store the syntax tree instead of the source code?

    - by Calmarius
    We have a lot of programming languages. Every language is parsed and syntax checked before translated into code so an abstract syntax tree is built. We have this abstract syntax tree, why don't we store this syntax tree instead of the source code (or next to the source code)? By using an AST instead of the source code. Every programmer in a team can serialize this tree to any language, they want (with the appropriate context free grammar) and parse back to AST when they finished. So this would eliminate the debate about the coding style questions (where to put the { and }, where to put whitespace, indentation, etc.) What are the pros and cons of this approach?

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  • Java+DOM: How do I convert a DOM tree without namespaces to a namespace-aware DOM tree?

    - by java.is.for.desktop
    Hello, everyone! I receive a Document (DOM tree) from a certain API (not in JDK). Sadly, this Document is not namespace-aware. As far as I know DOM, once generated, namespace-awareness can't be "added" afterwards. When converting this Document using a Transformer to a string, the XML is correct. Elements have xmlns:... attributes and name prefixes. But from the DOM point of view, there are no namespaces and no prefixes. I need to be able to convert this Document into a new Document which is namespace-aware. Yes, I could do this by just converting it to a string and back to DOM with namespaces enabled. But: nodes of the original tree have user-objects set. Converting to string and back would make a mapping of these user-objects to the new Document very complicated, if not impossible. So I really need a way to convert non-namespace DOM to namespace DOM. Are there any more-or-less straightforward solutions for this? Worst case (what I'm hoping to avoid) would be to manually iterate through old Document tree and create new namespace-aware Node for each old Node. Doing so, one had to manually "parse" namespace prefixes, watch out for xmlns-attributes, and maintain a mapping between prefixes and namespace-URIs. Lots of things to go wrong.

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  • ACL actions tag cause 'roles resource tree' draw incorrectly in admin/system/permissions/roles

    - by latvian
    Hi, We created new action similar to 'hold', 'ship' and others in the 'sales_order/view' admin section that can be triggered by clicking at the button. Afterward, we added our new action to the ACL with the following code in config.xml: <acl> <resources> <admin> <children> <sales> <children> <order> <children> <actions translate="title"> <title>Actions</title> <children> <shipNew translate="title"><title>Ship Ups</title></shipNew> </children> </actions> </children> <sort_order>10</sort_order> </order> </children> </sales> </children> </admin> </resources> </acl> ACL functionality works, however, in the 'Resources Tree'(System/Permissions/Roles/Role Resources) our new action does never show up as selected(checked) even thou it is allowed for particular Role. I can see that from table 'admin_rule' with resource id for our new action that it is allowed, so it needs to be selected, but it is not. When trying to solve this issue i looked into the template(permissions/rolesedit.phtml) and I found that the 'resource tree' is draw with Javascript...thats where i got stock due to my limited knowledge in Javascript. Why the resource tree does not display our new ACL entry correctly, that is the check box is never checked? Thank You for helping margots

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  • converting a Tree to newick format. java

    - by Esmond
    I'm having problems converting a binary rooted tree to newick format. The full explanation for such a format can be found: http://code.google.com/p/mrsrf/wiki/NewickTree An example of a newick format would be as follows: for a tree T such as http://www.cs.mcgill.ca/~cs251/OldCourses/1997/topic8/images/completetreetwo.gif the newick representation would be: (((8,9),(10,11)),((12,13),(14,15))) the internal node will become the commas while the leaves will be retained. such trees have internal nodes which will always have 2 children. I have a problem using recursion to come out with this newick format. The output contains far too many nodes and braces. Any comments to resolve this problem is appreciated or even an iterative algorithm would be welcomed import java.util.Stack; public class Tree { .... public String inOrderNewick(Node root, String output) throws ItemNotFoundException { if (root.hasChild()) { output += "("; output += inOrderNewick(root.child1, output); output += ","; output += inOrderNewick(root.child2, output); output += ")"; return output; } else { output += root.getSeq(); return output; } } }

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  • Realizing program with decision tree logics

    - by Vytas999
    The system realizes a game “Think animal”. Main use case is: 1. System offers user to think about any animal and the system will try to guess it 2. The system starts asking questions from the start of decision tree. Ex., “Question: It has fur?”, and provides possible answers – yes or no. 3. If the user answers Yes, the system proceeds to these steps: a. System tries to guess animal that has that feature, ex. “My guess: Is it bear?” and provides with possible answers – yes or no. b. If the user answer is Yes, the system offers to think off another animal 4. If the user answers is No, the system moves to No node in decision tree and moves to 2 step (and starts from asking from new node). 5. If system runs out of nodes (i.e., empty yes or no node was reached): a. the system announces that it has given up, and ask user to enter: i. What animal he had in mind ii. What is his characteristic feature b. User enters requested data c. The system creates a new node and links it to yes or no of last active node. Where i can get some information and some examples, when implementing decision tree logics in MS SQL Server and C#..? Any information will be usefull. Thanks

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  • Parse a CSV file using python (to make a decision tree later)

    - by Margaret
    First off, full disclosure: This is going towards a uni assignment, so I don't want to receive code. :). I'm more looking for approaches; I'm very new to python, having read a book but not yet written any code. The entire task is to import the contents of a CSV file, create a decision tree from the contents of the CSV file (using the ID3 algorithm), and then parse a second CSV file to run against the tree. There's a big (understandable) preference to have it capable of dealing with different CSV files (I asked if we were allowed to hard code the column names, mostly to eliminate it as a possibility, and the answer was no). The CSV files are in a fairly standard format; the header row is marked with a # then the column names are displayed, and every row after that is a simple series of values. Example: # Column1, Column2, Column3, Column4 Value01, Value02, Value03, Value04 Value11, Value12, Value13, Value14 At the moment, I'm trying to work out the first part: parsing the CSV. To make the decisions for the decision tree, a dictionary structure seems like it's going to be the most logical; so I was thinking of doing something along these lines: Read in each line, character by character If the character is not a comma or a space Append character to temporary string If the character is a comma Append the temporary string to a list Empty string Once a line has been read Create a dictionary using the header row as the key (somehow!) Append that dictionary to a list However, if I do things that way, I'm not sure how to make a mapping between the keys and the values. I'm also wondering whether there is some way to perform an action on every dictionary in a list, since I'll need to be doing things to the effect of "Everyone return their values for columns Column1 and Column4, so I can count up who has what!" - I assume that there is some mechanism, but I don't think I know how to do it. Is a dictionary the best way to do it? Would I be better off doing things using some other data structure? If so, what?

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  • Makefile; mirroring a growing tree through a process

    - by Martineau
    I would like to periodically mirror a growing tree, say, from $in to $out, doing a process in between (saving the only file header). As; #!/bin/bash in=./segd out=./db for f in `find $in -name "*.segd"`;do # Deduct output (dir + name) d=`dirname $f|perl -pe 's!'$in'!'$out'!'` n=`basename $f|perl -pe 's!$!_hdr!'` if [ ! -e $d/$n ]; then [ ! -d $d ] && mkdir -p $d; printf "From %s now build %s\n" $f "$d/$n" # Do something, whathever. For example e.g; dd if=$f bs=32 count=1 conv=swab 2>/dev/null|od -x > $d/$n fi done That is about fair. However; to be more robust, for a better synchronization (say if a source file did change or whatever), I would like to use a Makefile, as in; HDR := $(patsubst ./segd/%.segd,./db/%.segd_hdr,$(wildcard ./segd/*.segd)) all: ${HDR} db/%.segd_hdr: ./segd/%.segd echo "Doing" dd if=$< bs=32 count=1 conv=swab 2>/dev/null|od -x > $@ My problem; I cannot code this Makefile to "dive" more deeply within the source ./segd tree. How can we do it and is there a way ? Many thanks for your kind recommendations. PS: The idea will be to later rsync the (smaller) destination tree over a sat connection.

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  • Bidirectional real-time sync of large file tree between two distant linux servers

    - by dlo
    By large file tree I mean about 200k files, and growing all the time. A relatively small number of files are being changed in any given hour though. By bidirectional I mean that changes may occur on either server and need to be pushed to the other, so rsync doesn't seem appropriate. By distant I mean that the servers are both in data centers, but geographically remote from each other. Currently there are only 2 servers, but that may expand over time. By real-time, it's ok for there to be a little latency between syncing, but running a cron every 1-2 minutes doesn't seem right, since a very small fraction of files may change in any given hour, let alone minute. EDIT: This is running on VPS's so I might be limited on the kinds of kernel-level stuff I can do. Also, the VPS's are not resource-rich, so I'd shy away from solutions that require lots of ram (like Gluster?). What's the best / most "accepted" approach to get this done? This seems like it would be a common need, but I haven't been able to find a generally accepted approach yet, which was surprising. (I'm seeking the safety of the masses. :) I've come across lsyncd to trigger a sync at the filesystem change level. That seems clever though not super common, and I'm a bit confused by the various lsyncd approaches. There's just using lsyncd with rsync, but it seems this could be fragile for bidirectionality since rsync doesn't have a notion of memory (eg- to know whether a deleted file on A should be deleted on B or whether it's a new file on B that should be copied to A). lipsync appears to be just a lsyncd+rsync implementation, right? Then there's using lsyncd with csync2, like this: http://www.axivo.com/community/threads/lightning-fast-synchronization-with-csync2-and-lsyncd.121/ ... I'm leaning towards this approach, but csync2 is a little quirky, though I did do a successful test of it. I'm mostly concerned that I haven't been able to find a lot of community confirmation of this method. People on here seem to like Unison a lot, but it seems that it is no longer under active development and it's not clear that it has an automatic trigger like lsyncd. I've seen Gluster mentioned, but maybe overkill for what I need? UPDATE: fyi- I ended up going with the original solution I mentioned: lsyncd+csync2. It seems to work quite well, and I like the architectural approach of having the servers be very loosely joined, so that each server can operate indefinitely on its own regardless of the link quality between them.

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  • Explode all folders

    - by sam
    Ive got a folder with about a hundred sub folders and again each ones of those has between 10 and 20 sub folders, so all in all a pretty large folder tree. Is there a simple way i can explode or export all of the files in the tree to a new folder which will just be one folder contain the files (no folders, no trees). Im running OSX 10.8, although ive also got Parallels so if there is a windows solution i could just run that as its not something i need to do everyday.

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  • Constructing a Binary Tree from its traversals

    - by user991710
    I'm trying to construct a binary tree (unbalanced), given its traversals. I'm currently doing preorder + inorder but when I figure this out postorder will be no issue at all. I realize there are some question on the topic already but none of them seemed to answer my question. I've got a recursive method that takes the Preorder and the Inorder of a binary tree to reconstruct it, but is for some reason failing to link the root node with the subsequent children. Note: I don't want a solution. I've been trying to figure this out for a few hours now and even jotted down the recursion on paper and everything seems fine... so I must be missing something subtle. Here's the code: public static <T> BinaryNode<T> prePlusIn( T[] pre, T[] in) { if(pre.length != in.length) throw new IllegalArgumentException(); BinaryNode<T> base = new BinaryNode(); base.element = pre[0]; // * Get root from the preorder traversal. int indexOfRoot = 0; if(pre.length == 0 && in.length == 0) return null; if(pre.length == 1 && in.length == 1 && pre[0].equals(in[0])) return base; // * If both arrays are of size 1, element is a leaf. for(int i = 0; i < in.length -1; i++){ if(in[i].equals(base.element)){ // * Get the index of the root indexOfRoot = i; // in the inorder traversal. break; } // * If we cannot, the tree cannot be constructed as the traversals differ. else throw new IllegalArgumentException(); } // * Now, we recursively set the left and right subtrees of // the above "base" root node to whatever the new preorder // and inorder traversals end up constructing. T[] preleft = Arrays.copyOfRange(pre, 1, indexOfRoot + 1); T[] preright = Arrays.copyOfRange(pre, indexOfRoot + 1, pre.length); T[] inleft = Arrays.copyOfRange(in, 0, indexOfRoot); T[] inright = Arrays.copyOfRange(in, indexOfRoot + 1, in.length); base.left = prePlusIn( preleft, inleft); // * Construct left subtree. base.right = prePlusIn( preright, inright); // * Construc right subtree. return base; // * Return fully constructed tree } Basically, I construct additional arrays that house the pre- and inorder traversals of the left and right subtree (this seems terribly inefficient but I could not think of a better way with no helpers methods). Any ideas would be quite appreciated. Side note: While debugging it seems that the root note never receives the connections to the additional nodes (they remain null). From what I can see though, that should not happen... EDIT: To clarify, the method is throwing the IllegalArgumentException @ line 21 (else branch of the for loop, which should only be thrown if the traversals contain different elements.

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  • What is the usage of Splay Trees in the real world?

    - by Meena
    I decided to learn about balanced search trees, so I picked 2-3-4 and splay trees. What are the examples of splay trees usage in the real world? In this Cornell: http://www.cs.cornell.edu/courses/cs3110/2009fa/recitations/rec-splay.html I read that splay trees are 'A good example is a network router'. But from rest of the explanation seams like network routers use hash tables and not splay trees since the lookup time is constant instead of O(log n).

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  • What is the usage of Spaly Trees in the real world?

    - by Meena
    I decided to learn about Balance search trees, so I picked 2-3-4 and splay trees. I'm wondering what are the examples of splay trees usage in the real world? In this Cornell: http://www.cs.cornell.edu/courses/cs3110/2009fa/recitations/rec-splay.html I read that splay trees are 'A good example is a network router'. But from rest of the explanation seams like network routers use hash tables and not splay trees since the lookup time is constant instead of O(log n). thanks!

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  • Dynamic quadrees

    - by paul424
    recently I come out writing Quadtree for creatures culling in Opendungeons game. Thing is those are moving points and bounding hierarchy will quickly get lost if the quadtree is not rebuild very often. I have several variants, first is to upgrade the leaf position , every time creature move is requested. ( note if I would need collision detection anyway, so this might be necessery anyway). Second would be making leafs enough large , that the creature would sure stay inside it's bounding box ( due to its speed limit). The partition of a plane in quadtree is always fixed ( modulo the hierarchical unions of some parts) . For creatures close to the center of the plane , there would be no way of keeping it but inside one big leaf, besides this brokes the invariant that each point can be put into any small area as desired. So on the second thought could I use several quadrees ? Each would have its "coordinate axis XY" somwhere shifted ? Before I start playing with this maybe some other space diving structure would suit me better, unfortunetly wiki does not compare it's execution time : http://en.wikipedia.org/wiki/Grid_%28spatial_index%29#See_also

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  • Fast language for problem solving? [closed]

    - by Friend of Kim
    I learned PHP to make websites. After some years I've started using programming for solving what is difficult tasks for my level. Now I want to make a program that solves equations. (I want to write it myself, not use an API. Because I'm doing this for the sake of the challenge, not for the result..) Because of this, I'm going to learn a new and faster/better language. It's going to be C++, Java, Python or C#. What are the benefits of each language, and which language is best for speed compared to speed of writing and readability? Using C would be lightning fast, but the lack of OO is making for more complex code and reduces the readability, for example..

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  • async tree jquery easy ui

    - by user765368
    I'm trying to create an Async Tree in jQuery Easy Ui. I understand the idea behind it, but will this work if my root node is not a node that is coming from the database or something (therefore, it does not have any id). My root node is some node that I define myself. How would I make an async tree in jquery easy ui to load a bunch of nodes as children of my root node (which, again has no id because it's not coming from the database. My children nodes are coming from the database though). I hope y'all understand what I'm trying to do here. Any help please

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  • Tree View / File View Control for C#

    - by Jason
    I have been looking for a C# tree control for displaying a file system that has the following capabilities: Select a starting directory. I don't always want to start at a "default" top directory level. The ability to grab an event when the user double clicks on a file in the tree. I want to handle opening the file within my application. I have been looking at this C# File Browser. Unfortunately, I have not been able to figure out how to do meet my second need. (If anybody can clear that up for me, I would like that even better.) Thanks for any help.

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  • complicated graphviz tree structure

    - by thomas
    Hello. I am trying to create a tree structure with graphviz. I am open to either writing the graphviz code by hand or using the ruby-graphviz gem for ruby. Given the below picture can anyone provide any insight on the necessary code? Ignore that the lines are not straight...they should be when graphviz builds the graph. I am open to having dots/points when lines intersect as well. I have played with ruby-graphviz and the family tree class...this is getting me part of the way there but I really need all lines to be straight and intersect at right angles and the out-of-the-box code doesn't seem to do that.

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  • JavaScript tree / treegrid libraries

    - by desau
    I'm looking for a good JavaScript tree / treegrid package. Now -- before you answer: It needs to be able to perform well with lots of nodes. Perhaps 1,000 sibling nodes. It needs to be able to draw to a usable state within 2 or 3 seconds with 1,000 nodes. It doesn't necessarily need to draw all 1,000 nodes at once -- if it supports some sort of "smart rendering" or fake scrolling. Beyond that, column resizing, drag and drop, inline editing would all be nice, although I could probably add that functionality myself. I've already tried dojo's tree and yahoo's YUI treeview. Both are too slow.

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  • Build and render infinite hierarchical category tree from self-referential category table

    - by FreshCode
    I have a Categories table in which each category has a ParentId that can refer to any other category's CategoryId that I want to display as multi-level HTML list, like so: <ul class="tree"> <li>Parent Category <ul> <li>1st Child Category <!-- more sub-categories --> </li> <li>2nd Child Category <!-- more sub-categories --> </li> </ul> </li> </ul> Presently I am recursively rendering a partial view and passing down the next category. It works great, but it's wrong because I'm executing queries in a view. How can I render the list into a tree object and cache it for quick display every time I need a list of all hierarchical categories?

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  • MS SQL server and Trees

    - by Julian
    Im looking for some way of extrating data form a tree table as defined below. Table Tree Defined as :- TreeID uniqueidentifier TreeParent uniqueidentifier TreeCode varchar(50) TreeDesc varchar(100) Data some (23k rows), Parent Refs back into ID in table The following SQL renders the whole tree (takes arround 2 mins 30) I need to do the following. 1) Render each Tree Node with its LVL 1 parent 2) Render all nodes that have a Description that matches a TreeDesc like 'SomeText%' 3) Render all parent nodes that are for a single tree id. Items 2 and 3 take 2mins30 so this needs to be a lot faster! Item 1, just cant work out how to do it with out killing SQL or taking forever any sugestions would be helpfull Thanks Julian WITH TreeCTE(TreeCode, TreeDesc, depth, TreeParent, TreeID) AS ( -- anchor member SELECT cast('' as varchar(50)) as TreeCode , cast('Trees' as varchar(100)) as TreeDesc, cast('0' as Integer) as depth, cast('00000000-0000-0000-0000-000000000000' as uniqueidentifier) as TreeParent, cast('00000000-0000-0000-0000-000000000000' as uniqueidentifier) as TreeID UNION ALL -- recursive member SELECT s.TreeCode, s.TreeDesc, cte.depth+1, isnull(s.TreeParent, cast('00000000-0000-0000-0000-000000000000' as uniqueidentifier)), isnull(s.TreeID, cast('00000000-0000-0000-0000-000000000000' as uniqueidentifier)) FROM pdTrees AS S JOIN TreeCTE AS cte ON isnull(s.TreeParent, cast('00000000-0000-0000-0000-000000000000' as uniqueidentifier)) = isnull( cte.TreeID , cast('00000000-0000-0000-0000-000000000000' as uniqueidentifier)) ) -- outer query SELECT s.TreeID, s.TreeCode, s.TreeDesc, s.depth, s.TreeParent FROM TreeCTE s

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  • Code to apply expression tree directly to List

    - by Gamma Vega
    Is there a method call in Linq that will apply a expression tree directly on a List<V>? For instance, if I have a expression tree that is built on Order type, and i have a collection of List<Order> items on which i need to apply this expression. I am looking something similar to: class OrderListStore : IQueryable<V>, <other interfaces required to implement custom linq provider> { List<Order> orders; public Expression Expression { get { return Expression.Constant(this); } } IEnumerator<V> IEnumerable<V>.GetEnumerator() { //Here I need to have a method that will take the existing expression //and directly apply on list something like this .. Expression.Translate(orders); } } Any help in this regard is highly appreciated.

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