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  • help in the Donalds B. Johnson's algorithm, i cannot understand the pseudo code (PART II)

    - by Pitelk
    Hi all , i cannot understand a certain part of the paper published by Donald Johnson about finding cycles (Circuits) in a graph. More specific i cannot understand what is the matrix Ak which is mentioned in the following line of the pseudo code : Ak:=adjacency structure of strong component K with least vertex in subgraph of G induced by {s,s+1,....n}; to make things worse some lines after is mentins " for i in Vk do " without declaring what the Vk is... As far i have understand we have the following: 1) in general, a strong component is a sub-graph of a graph, in which for every node of this sub-graph there is a path to any node of the sub-graph (in other words you can access any node of the sub-graph from any other node of the sub-graph) 2) a sub-graph induced by a list of nodes is a graph containing all these nodes plus all the edges connecting these nodes. in paper the mathematical definition is " F is a subgraph of G induced by W if W is subset of V and F = (W,{u,y)|u,y in W and (u,y) in E)}) where u,y are edges , E is the set of all the edges in the graph, W is a set of nodes. 3)in the code implementation the nodes are named by integer numbers 1 ... n. 4) I suspect that the Vk is the set of nodes of the strong component K. now to the question. Lets say we have a graph G= (V,E) with V = {1,2,3,4,5,6,7,8,9} which it can be divided into 3 strong components the SC1 = {1,4,7,8} SC2= {2,3,9} SC3 = {5,6} (and their edges) Can anybody give me an example for s =1, s= 2, s= 5 what if going to be the Vk and Ak according to the code? The pseudo code is in my previous question in http://stackoverflow.com/questions/2908575/help-in-the-donalds-b-johnsons-algorithm-i-cannot-understand-the-pseudo-code and the paper can be found at http://stackoverflow.com/questions/2908575/help-in-the-donalds-b-johnsons-algorithm-i-cannot-understand-the-pseudo-code thank you in advance

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  • Reading graph inputs for a programming puzzle and then solving it

    - by Vrashabh
    I just took a programming competition question and I absolutely bombed it. I had trouble right at the beginning itself from reading the input set. The question was basically a variant of this puzzle http://codercharts.com/puzzle/evacuation-plan but also had an hour component in the first line(say 3 hours after start of evacuation). It reads like this This puzzle is a tribute to all the people who suffered from the earthquake in Japan. The goal of this puzzle is, given a network of road and locations, to determine the maximum number of people that can be evacuated. The people must be evacuated from evacuation points to rescue points. The list of road and the number of people they can carry per hour is provided. Input Specifications Your program must accept one and only one command line argument: the input file. The input file is formatted as follows: the first line contains 4 integers n r s t n is the number of locations (each location is given by a number from 0 to n-1) r is the number of roads s is the number of locations to be evacuated from (evacuation points) t is the number of locations where people must be evacuated to (rescue points) the second line contains s integers giving the locations of the evacuation points the third line contains t integers giving the locations of the rescue points the r following lines contain to the road definitions. Each road is defined by 3 integers l1 l2 width where l1 and l2 are the locations connected by the road (roads are one-way) and width is the number of people per hour that can fit on the road Now look at the sample input set 5 5 1 2 3 0 3 4 0 1 10 0 2 5 1 2 4 1 3 5 2 4 10 The 3 in the first line is the additional component and is defined as the number of hours since the resuce has started which is 3 in this case. Now my solution was to use Dijisktras algorithm to find the shortest path between each of the rescue and evac nodes. Now my problem started with how to read the input set. I read the first line in python and stored the values in variables. But then I did not know how to store the values of the distance between the nodes and what DS to use and how to input it to say a standard implementation of dijikstras algorithm. So my question is two fold 1.) How do I take the input of such problems? - I have faced this problem in quite a few competitions recently and I hope I can get a simple code snippet or an explanation in java or python to read the data input set in such a way that I can input it as a graph to graph algorithms like dijikstra and floyd/warshall. Also a solution to the above problem would also help. 2.) How to solve this puzzle? My algorithm was: Find shortest path between evac points (in the above example it is 14 from 0 to 3) Multiply it by number of hours to get maximal number of saves Also the answer given for the variant for the input set was 24 which I dont understand. Can someone explain that also. UPDATE: I get how the answer is 14 in the given problem link - it seems to be just the shortest path between node 0 and 3. But with the 3 hour component how is the answer 24 UPDATE I get how it is 24 - its a complete graph traversal at every hour and this is how I solve it Hour 1 Node 0 to Node 1 - 10 people Node 0 to Node 2- 5 people TotalRescueCount=0 Node 1=10 Node 2= 5 Hour 2 Node 1 to Node 3 = 5(Rescued) Node 2 to Node 4 = 5(Rescued) Node 0 to Node 1 = 10 Node 0 to Node 2 = 5 Node 1 to Node 2 = 4 TotalRescueCount = 10 Node 1 = 10 Node 2= 5+4 = 9 Hour 3 Node 1 to Node 3 = 5(Rescued) Node 2 to Node 4 = 5+4 = 9(Rescued) TotalRescueCount = 9+5+10 = 24 It hard enough for this case , for multiple evac and rescue points how in the world would I write a pgm for this ?

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  • Problem with OOP Class Definitions

    - by oben
    Hi, this is Oben from Turkey. I work for my homework in C++ and i have some problems with multiply definitions. My graph class ; class Graph{ private: string name; //Graph name fstream* graphFile; //Graph's file protected: string opBuf; //Operations buffer int containsNode(string); //Query if a node is present Node* nodes; //Nodes in the graph int nofNodes; //Number of nodes in the graph public: static int nOfGraphs; //Number of graphs produced Graph(); //Constructors and destructor Graph(int); Graph(string); Graph(const Graph &); ~Graph(); string getGraphName(); //Get graph name bool addNode(string); //add a node to the graph bool deleteNode(string); //delete a node from the graph bool addEdge(string,string); //add an edge to the graph bool deleteEdge(string,string); //delete an edge from the graph void intersect(const Graph&); //intersect the graph with the <par> void unite(const Graph&); //intersect the graph with the <par> string toString(); //get string representation of the graph void acceptTraverse(BreadthFirst*); void acceptTraverse(DepthFirst *); }; and my traversal class; class Traversal { public: string *visitedNodes; virtual string traverse (const Graph & ); }; class BreadthFirst : public Traversal { public : BreadthFirst(); string traverse(); }; class DepthFirst : public Traversal { public : DepthFirst(); string traverse(); }; My problem is in traversal class , i need to declare Graph class at the same time , in graph class i need traversal class to declare. I have big problems with declerations :) Could you please help me ?

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  • Reverse Bredth First Search in C#

    - by Ngu Soon Hui
    Anyone has a ready implementation of the Reverse Bredth First Search algorithm in C#? By Reverse Bredth First Search, I mean instead of searching a tree starting from a common node, I want to search the tree from the bottom and gradually converged to a common node. Let's see the below figure, this is the output of a Bredth First Search: In my reverse bredth first search, 9,10,11 and 12 will be the first few nodes found ( the order of them are not important as they are all first order). 5, 6, 7 and 8 are the second few nodes found, and so on. 1 would be the last node found. Any ideas or pointers?

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  • Reverse Breadth First traversal in C#

    - by Ngu Soon Hui
    Anyone has a ready implementation of the Reverse Breadth First traversal algorithm in C#? By Reverse Breadth First traversal , I mean instead of searching a tree starting from a common node, I want to search the tree from the bottom and gradually converged to a common node. Let's see the below figure, this is the output of a Breadth First traversal : In my reverse breadth first traversal , 9,10,11 and 12 will be the first few nodes found ( the order of them are not important as they are all first order). 5, 6, 7 and 8 are the second few nodes found, and so on. 1 would be the last node found. Any ideas or pointers? Edit: Change "Breadth First Search" to "Breadth First traversal" to clarify the question

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  • Reverse Breath First Search in C#

    - by Ngu Soon Hui
    Anyone has a ready implementation of the Reverse Breath First Search algorithm in C#? By Reverse Breath First Search, I mean instead of searching a tree starting from a common node, I want to search the tree from the bottom and gradually converged to a common node. Let's see the below figure, this is the output of a Breath First Search: In my reverse breath first search, 9,10,11 and 12 will be the first few nodes found ( the order of them are not important as they are all first order). 5, 6, 7 and 8 are the second few nodes found, and so on. 1 would be the last node found. Any ideas or pointers?

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  • directed unweighted graphs C

    - by fang_dejavu
    Hi, I'm planning to write a program in C that builds the adjacency list, performs the depth first search, performs the breadth first search, and performs the topological sort. Where can I get some info about this subject in C? Any help is appreciated

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  • Drawing Directed Acyclic Graphs: Using DAG property to improve layout/edge routing?

    - by Robert Fraser
    Hi, Laying out the verticies in a DAG in a tree form (i.e. verticies with no in-edges on top, verticies dependent only on those on the next level, etc.) is rather simple. However, is there a simple algorithm to do this that minimizes edge crossing? (For some graphs, it may be impossible to completely eliminate edge crossing.) A picture says a thousand words, so is there an algorithm that would suggest: instead of:

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  • Graph navigation problem

    - by affan
    I have graph of components and relation between them. User open graph and want to navigate through the graph base on his choice. He start with root node and click expand button which reveal new component that is related to current component. The problem is with when use decide to collapse a node. I have to choose a sub-tree to hide and at same time leave graph in consistent state so that there is no expanded node with missing relation to another node in graph. Now in case of cyclic/loop between component i have difficult of choosing sub-tree. For simplicity i choose the order in which they were expanded. So if a A expand into B and C collapse A will hide the nodes and edge that it has created. Now consider flowing scenario. [-] mean expanded state and [+] mean not yet expanded. A is expanded to reveal B and C. And then B is expanded to reveal D. C is expanded which create a link between C and exiting node D and also create node E. Now user decide to collapse B. Since by order of expansion D is child of B it will collapse and hide D. This leave graph in inconsistent state as C is expanded with edge to D but D is not anymore there if i remove CD edge it will still be inconsistent. If i collapse C. And E is again a cyclic link e.g to B will produce the same problem. /-----B[-]-----\ A[-] D[+] \-----C[-]-----/ \ E[+] So guys any idea how can i solve this problem. User need to navigate through graph and should be able to collapse but i am stuck with problem of cyclic nodes in which case any of node in loop if collapse will leave graph in inconsistent state.

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  • Data structure for bubble shooter game

    - by SundayMonday
    I'm starting to make a bubble shooter game for a mobile OS. Assume this is just the basic "three or more same-color bubbles that touch pop" and all bubbles that are separated from their group fall/pop. What data structures are common for storing the bubbles? I've considered using an undirected, connected graph where each node is a bubble. This seems like it could help answer the question "which bubbles (if any) should fall now?" after some arbitrary bubbles are popped and corresponding nodes are removed from the graph. I think the answer is all bubbles that were just disconnected from the graph should fall. However the graph approach might be overkill so I'm not sure. Another consideration for the data structure is collision detection. Perhaps being able to grab a list of neighboring bubbles in constant time for a particular "bubble slot" is useful. So the collision detection would be something like "moving bubble is closest to slot ij, neighbors of slot ij are bubbles a,b,c, moving bubble is sufficiently close to bubble b hence moving bubble should come to rest in slot ij". A game like this could be probably be made with a relatively crude grid structure as the primary data structure. However it seems like answering "which bubbles (if any) should fall now?" would be trickier with this data structure.

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  • How do find the longest path in a cyclic Graph between two nodes?

    - by Nazgulled
    Hi, I already solved most the questions posted here, all but the longest path one. I've read the Wikipedia article about longest paths and it seems any easy problem if the graph was acyclic, which mine is not. How do I solve the problem then? Brute force, by checking all possible paths? How do I even begin to do that? I know it's going to take A LOT on a Graph with ~18000. But I just want to develop it anyway, cause it's required for the project and I'll just test it and show it to the instructor on a smaller scale graph where the execution time is just a second or two. At least I did all tasks required and I have a running proof of concept that it works but there's no better way on cyclic graphs. But I don't have clue where to start checking all these paths...

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  • Neo4j Performing shortest path calculations on stored data

    - by paddydub
    I would like to store the following graph data in the database, graph.makeEdge( "s", "c", "cost", (double) 7 ); graph.makeEdge( "c", "e", "cost", (double) 7 ); graph.makeEdge( "s", "a", "cost", (double) 2 ); graph.makeEdge( "a", "b", "cost", (double) 7 ); graph.makeEdge( "b", "e", "cost", (double) 2 ); Then run the Dijskra algorighm from a web servlet, to find shortest path calculations using the stored graph data. Then I will print the path to a html file from the servlet. Dijkstra<Double> dijkstra = getDijkstra( graph, 0.0, "s", "e" );

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  • Location tagging facebook open graph actions so that only friends in that location view in their feeds

    - by Arvind Srinivasan
    Is there a way to tag open graph actions so as to target certain recipients and not others? For example, if my app talks about new coffee shop openings in various cities, is there a way to publish the 'opening' action to the graph, perhaps with location / coordinates, such that this is only seen by friends in that locality? I really don't want to spam my friends in London about an opening I'm excited about in Portland. How can I help facebook with the feed relevance in these cases? I noticed that there is a "place" property on open graph objects - could this somehow be used?

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  • In a graph, how to find the nearest node to a group of nodes?

    - by Nikola
    Hello, I have an undirected, unweighted graph, which doesn't have to be planar. I also have a subset of graph's nodes (true subset) and I need to find a node not belonging to the subset, with minimum sum of distances to all nodes in the subset. So far, I have implemented breath-first search starting from each node in the subset, and the intersection that occurs first is the node I am looking for. Unfortunately, it is running too slow since the graph contains a large number of nodes. Any advice or comment will be appreciated. Thank you, Nikola

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  • How to detect if breaking an edge will make a graph disjoint?

    - by the_graph_guy
    I have a graph that starts off with a single, root node. Nodes are added one by one to the graph. At node creation time, they have to be linked either to the root node, or to another node, by a single edge. Edges can also be created and deleted (one by one, between any two nodes). Nodes can be deleted one at a time. Node and edge creation, deletion operations can happen in any arbitrary order. OK, so here's my question: When an edge is deleted, is it possible do determine, in constant time (i.e. with an O(1) algorithm), if doing this will divide the graph into two disjoint subgraphs? If it will, then which side of the edge will the root node belong? I'm willing to maintain, within reasonable limits, any additional data structure that can facilitate the derivation of this information. Maybe it is not possible to do it in O(1), if so any pointers to literature will be appreciated.

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  • Google Analytics show zero for "Search Engine Optimizations" graph

    - by Saeed Neamati
    In Google Analytics new design, there is an area related to the queries and impressions related to your site. You can get there by following Traffic Sources = Search Engine Optimization = Queries. However, it now shows zero for the "Site Usage" graph, at the top section, while other areas of Google Analytics definitely show that site has visitors and has been used. No matter how much I search, I can't find the source of the problem. Does anyone know where the problem might be?

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  • How to view the filter graph used by Windows Media Player

    - by Ian Boyd
    i have a video that i cannot render in Graph Edit: GSpot cannot render: and AVISynth's DirectShowSource cannot open: And yet Windows Media Player (12) can play it fine. How can i figure out the filters that Windows Media Player is using, when DirectShow itself cannot render the file? i tried running GraphEdit as an adminstrator and connecting to a remote graph, but Windows Media Player does not register its graph in the running objects table: Related question: How can i access a file in AviSynth that Windows Media Player can play, but DirectShow cannot?

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  • Simple tool to graph memory usage?

    - by dbr
    Is there a script that will show memory usage as a graph, for example as a pie-chart, with each process being being a separate slice? I'm not looking for something like Munin to graph memory usage over time, but rather show the memory usage per-process at a single point in time. To make my request even more obscure, it is for a headless server (so no X applications). The simplest way would be to write a PNG file, or possibly an HTML file (which could use Javascript to allow the filtering of processes, changing between graph-types and so on)

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  • EC2 instance store cloning or to ebs via guy management console

    - by devnull
    I have found similar questions here but the answer are either outdated or are from the command line. The case is this. I have an EC2 instance using instance store (this was the only AMI available for Debian 6 in Ireland). Now through the AWS GUI I can do a snapshot of the instance volume and/or even create a volume. But an image made from the snapshot doesn't boot. What is the best solution to either clone an EC2 instance that uses instance store OR from the created snapshot of the instance store to launch a new EBS instance (identical clone) FROM the gui aws management console and not command line ? Before turning this down consider that there is not similar question on how to do it via the aws management console. hint can't be done is not an appropriate answer. As you can create a snapshot of the instance store backed instance and/or a volume and create an AMI from that snapshot.

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  • MRTG + RRDTool Hourly Graph

    - by SuperMicro321
    I am using MRTG + RRDtool to monitor the bandwidth on each switchport of a Cisco Catalyst 2950 via snmp. Is MRTG capable of generating an hourly graph? With RRDtool I was able to set the interval to 1 minute in hopes of getting a more detailed graph, but the shortest timeframe the graph is 'Daily' graph (5 Minute Average) and the image is too small. What I am looking to get out of this: I am looking to be able to visually monitor all of the switch ports and tell when port begins to have unusually high traffic, in real time (1 minute interval of snmp poll, graphs generated, and page refreshed).

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