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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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  • Tree data structure gems compared?

    - by huug
    I want to you use a tree structure for my navigation. I was thinking about using Ancestry, but then I found this article about 7 plugins for providing a tree structure to your models. What are the pros/cons for each plugin/gem and above all: which one do you recommend? Tnx!

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  • Can a variable like 'int' be considered a primitive/fundamental data structure?

    - by Ravi Gupta
    A rough definition of a data structure is that it allows you to store data and apply a set of operations on that data while preserving consistency of data before and after the operation. However some people insist that a primitive variable like 'int' can also be considered as a data structure. I get that part where it allows you to store data but I guess the operation part is missing. Primitive variables don't have operations attached to them. So I feel that unless you have a set of operations defined and attached to it you cannot call it a data structure. 'int' doesn't have any operation attached to it, it can be operated upon with a set of generic operators. Please advise if I got something wrong here.

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  • Collision free hash function for a specific data structure

    - by Max
    Is it possible to create collision free hash function for a data structure with specific properties. The datastructure is int[][][] It contains no duplicates The range of integers that are contained in it is defined. Let's say it's 0..1000, the maximal integer is definitely not greater than 10000. Big problem is that this hash function should also be very fast. Is there a way to create such a hash function? Maybe at run time depending on the integer range?

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  • find the top K most frequent numbers in a data stream

    - by Jin
    This is more of a data structure question rather than a coding question. If I am fetching a data stream, i.e, I keep receiving float numbers once at a time, how should I keep track of the top K frequent numbers? Here my memory is 4G and I prefer to have less communication with hard drive unless necessary. I think heap is good for updating the max and min. How should I design the data structure? Thanks

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  • Clojure: I have many sorted maps and want to reduce in order all there values a super maps of keys -> vector

    - by Alex Foreman
    I have seen this but can't work out how to apply it (no pun intended) to my situation. I have a sorted list of maps like this: (note there can be more than two keys in the map) ({name1 3, name2 7}, {name1 35, name2 7}, {name1 0, name2 3}) What I am after is this data structure afterwards: ({:name1 [3,35,0]}, {:name2 [7,7,3]}) Ive been struggling with this for a while and cant seem to get anywhere near. Caveats: The data must stay sorted and I have N keywords not just two.

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  • What's the name of the storage paradigm that uses cubes subdivided into 8 smaller cubes ad infinitum?

    - by Eric
    If I have a cube divided into 8 smaller cubes, each of which may be subdivided into a further 8 cubes, ad infinitum, what is the name of my system? I know that it's a special case of a tree, where each brance contains exactly 8 other leaves/branches. I remember the name starting with "Oct", and there was a wikipedia article on it, but I honestly can't find it! Does anyone know what such a data structure is actually known as?

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  • Inserting a number into a sorted array!

    - by Jay
    I would like to write a piece of code for inserting a number into a sorted array at the appropriate position (i.e. the array should still remain sorted after insertion) My data structure doesn't allow duplicates. I am planning to do something like this: 1. Find the right index where I should be putting this element using binary search 2. Create space for this element, by moving all the elements from that index down. 3. Put this element there. Is there any other better way?

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  • Algorithm: Find smallest subset containing K 0's

    - by Vishal
    I have array of 1's and 0's only. Now I want to find contiguous subset/subarray which contains at least K 0's. Example Array is 1 1 0 1 1 0 1 1 0 0 0 0 1 0 1 1 0 0 0 1 1 0 0 1 0 0 0 and K(6) should be 0 0 1 0 1 1 0 0 0 or 0 0 0 0 1 0 1 1 0.... My Solution Array: 1 1 0 1 1 0 1 1 0 0 0 0 1 0 1 1 0 0 0 1 1 0 0 Index: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Sum: 1 2 2 3 4 4 5 6 6 6 6 6 7 7 8 9 9 9 9 10 11 11 11 Diff(I-S): 0 0 1 1 1 2 2 2 3 4 5 6 6 7 7 7 8 9 10 10 10 11 12 For K(6) Start with 9-15 = Store difference in diff. Next increase difference 8-15(Difference in index) 8-14(Compare Difference in index) So on keep moving to find element with least elements... I am looking for better algorithm for this solution.

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  • Random begining index iterator for HashSet

    - by funktku
    I use HashSet for add(); remove(); clear(); iterator(); methods. So far everything worked like a charm. However, now I need to fulfill a different requirement. I'd like to be able to start iterating from a certain index. For example, I'd like the following two programs to have same output. Program 1 Iterator it=map.iterator(); for(int i=0;i<100;i++) { it.next(); } while (it.hasNext()) { doSomethingWith(it.next()); } Program 2 Iterator it=map.iterator(100); while (it.hasNext()) { doSomethingWith(it.next()); } The reason I don't want to use the Program 1 is that it creates un-neccesary overhead. From my researchs, I couldn't not find a practical way of creating an iterator with begining index. So, my question is, what would be a good way to achieve my goal while minimizing the overheads? Thank you.

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  • How can I read and parse chunks of data into a Perl hash of arrays?

    - by neversaint
    I have data that looks like this: #info #info2 1:SRX004541 Submitter: UT-MGS, UT-MGS Study: Glossina morsitans transcript sequencing project(SRP000741) Sample: Glossina morsitans(SRS002835) Instrument: Illumina Genome Analyzer Total: 1 run, 8.3M spots, 299.9M bases Run #1: SRR016086, 8330172 spots, 299886192 bases 2:SRX004540 Submitter: UT-MGS Study: Anopheles stephensi transcript sequencing project(SRP000747) Sample: Anopheles stephensi(SRS002864) Instrument: Solexa 1G Genome Analyzer Total: 1 run, 8.4M spots, 401M bases Run #1: SRR017875, 8354743 spots, 401027664 bases 3:SRX002521 Submitter: UT-MGS Study: Massive transcriptional start site mapping of human cells under hypoxic conditions.(SRP000403) Sample: Human DLD-1 tissue culture cell line(SRS001843) Instrument: Solexa 1G Genome Analyzer Total: 6 runs, 27.1M spots, 977M bases Run #1: SRR013356, 4801519 spots, 172854684 bases Run #2: SRR013357, 3603355 spots, 129720780 bases Run #3: SRR013358, 3459692 spots, 124548912 bases Run #4: SRR013360, 5219342 spots, 187896312 bases Run #5: SRR013361, 5140152 spots, 185045472 bases Run #6: SRR013370, 4916054 spots, 176977944 bases What I want to do is to create a hash of array with first line of each chunk as keys and SR## part of lines with "^Run" as its array member: $VAR = { 'SRX004541' => ['SRR016086'], # etc } But why my construct doesn't work. And it must be a better way to do it. use Data::Dumper; my %bighash; my $head = ""; my @temp = (); while ( <> ) { chomp; next if (/^\#/); if ( /^\d{1,2}:(\w+)/ ) { print "$1\n"; $head = $1; } elsif (/^Run \#\d+: (\w+),.*/){ print "\t$1\n"; push @temp, $1; } elsif (/^$/) { push @{$bighash{$head}}, [@temp]; @temp =(); } } print Dumper \%bighash ;

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  • How can I declare a pointer structure using {}?

    - by Y_Y
    This probably is one of the easiest question ever in C programming language... I have the following code: typedef struct node { int data; struct node * after; struct node * before; }node; struct node head = {10,&head,&head}; Is there a way I can make head to be *head [make it a pointer] and still have the availability to use '{ }' [{10,&head,&head}] to declare an instance of head and still leave it out in the global scope? For example: //not legal!!! struct node *head = {10,&head,&head};

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  • Python - a clean approach to this problem?

    - by Seafoid
    Hi, I am having trouble picking the best data structure for solving a problem. The problem is as below: I have a nested list of identity codes where the sublists are of varying length. li = [['abc', 'ghi', 'lmn'], ['kop'], ['hgi', 'ghy']] I have a file with two entries on each line; an identity code and a number. abc 2.93 ghi 3.87 lmn 5.96 Each sublist represents a cluster. I wish to select the i.d. from each sublist with the highest number associated with it, append that i.d. to a new list and ultimately write it to a new file. What data structure should the file with numbers be read in as? Also, how would you iterate over said data structure to return the i.d. with the highest number that matches the i.d. within a sublist? Thanks, S :-)

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  • How does including a .csv work in an enum?

    - by Tommy
    enum ID // IDs { ID_HEADER = 0, // ID 0 = headers #include "DATA.CSV" ID_LIMIT }; I inherited some code here..... Looking at "DATA.CSV" I see all the ID's used to populate the enum in column B, along with other data. My question: How does the enum know that it is using "column B" to retrieve it's members? There must be some other logic in the application yet I don't see it. What else should I look for? Thanks.

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  • How is push()ing and pop()ping defined?

    - by Helper Method
    I know how the push() and pop() methods in a typical implementation of a Queue/Linked List work but what I do want to know is what you actually define as a push or a pop? When can you name a method push()/pop()? What makes the insert()/add() method in a typical Tree implementation not a push()? My understanding is that push()ing means putting something to a position some special pointer is pointing to, and pop()ping an element means putting some object away some pointer is pointing to, but it doesn't seem to be clearly defined. Or does the naming matter at all?

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  • algorithm to make easy my job

    - by gcc
    Iwill tell part of study material task but, dont afraid, I dont want write all of them , I will ask just specific question.okey; User will give me a function with three unknown. example: sin(a+b)+ln(5)*(log(ab)-32/sqrt(abc)) another example for function atan(23/a)-exp(a,b)*(123+asin(ac)) and there are some another input with funtion but in all input a,b and c, are doesnot determined, Anyway,I wont tell the other part,I just asking how I should take the fuction such that I can do my job with easy?

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  • why use the "!!!"?

    - by lazyanno
    as follow codes: var a = {}; if(!!!a[tabType]){ a[tabType] = []; a[tabType].push([self,boxObj]); }else{ a[tabType].push([self,boxObj]); } i think !!!a[tabType] equals !a[tabType] why use the "!!!" not "!" ? thank you!

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  • Hash Tables - Java

    - by Antony
    Am about to do a homework, and i need to store quite a lot of information (Dictionary) in a data structure of my choice. I heard people in my classroom saying hash-tables are the way to go. How come?

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  • MATLAB: What is an appropriate Data Structure for a Matrix with Random Variable Entries?

    - by user568249
    I'm currently working in an area that is related to simulation and trying to design a data structure that can include random variables within matrices. To motivate this let me say I have the following matrix: [a b; c d] I want to find a data structure that will allow for a, b, c, d to either be real numbers or random variables. As an example, let's say that a = 1, b = -1, c = 2 but let d be a normally distributed random variable with mean 0 and SD 1. The data structure that I have in mind will give no value to d. However, I also want to be able to design a function that can take in the structure, simulate an uniform(0,1), obtain a value for d using an inverse CDF and then spit out an actual matrix. I have several ideas to do this (all related to the MATLAB icdf function) but would like to know how more experienced programmers would do this. In this application, it's important that the structure is as "lean" as possible since I will be working with very very large matrices and memory will be an issue.

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  • Structure of Astar (A*) graph search data in C#

    - by Shawn Mclean
    How do you structure you graphs/nodes in a graph search class? I'm basically creating a NavMesh and need to generate the nodes from 1 polygon to the other. The edge that joins both polygons will be the node. I'll then run A* on these Nodes to calculate the shortest path. I just need to know how to structure my classes and their properties? I know for sure I wont need to create a fully blown undirected graph with nodes and edges.

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  • Purely functional equivalent of weakhashmap?

    - by Jon Harrop
    Weak hash tables like Java's weak hash map use weak references to track the collection of unreachable keys by the garbage collector and remove bindings with that key from the collection. Weak hash tables are typically used to implement indirections from one vertex or edge in a graph to another because they allow the garbage collector to collect unreachable portions of the graph. Is there a purely functional equivalent of this data structure? If not, how might one be created? This seems like an interesting challenge. The internal implementation cannot be pure because it must collect (i.e. mutate) the data structure in order to remove unreachable parts but I believe it could present a pure interface to the user, who could never observe the impurities because they only affect portions of the data structure that the user can, by definition, no longer reach.

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  • Would this predicate work ? this came on my quiz to find the position of element X in a data structure called list

    - by M.K
    example: position(1,list(1,list(2,nil)),Z). Z = 1. position(3,list(1,list(2,list(3,nil)),Z). Z = 3. where Z is the position of element X in a data structure of a list in the above format Here was my solution: position(X,list(nil),0). %empty list position(X,list(X,T),1). %list with X as head or first element position(X,list(H,T),Z):- position(X,list(T,nil),Z1), %X is in tail of list (H,T) Z is Z1 + 1.

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  • A question on getting number of nodes in a Binary Tree

    - by Robert
    Dear all, I have written up two functions (pseudo code) for calculation the number of nodes and the tree height of a Binary Tree,given the root of the tree. Most importantly,the Binary Tree is represented as the First chiled/next sibling format. so struct TreeNode { Object element; TreeNode *firstChild; TreeNode *nextSibling; } Calculate the # of nodes: public int countNode(TreeNode root) { int count=0; while(root!=null) { root= root.firstChild; count++; } return count; } public int countHeight(TreeNode root) { int height=0; while(root!=null) { root= root.nextSibling; height++; } return height; } This is one of the problem I saw on an algorithm book,and my solution above seems to have some problems,also I didn't quite get the points of using this First Child/right sibling representation of Binary Tree,could you guys give me some idea and feedback,please? Cheers!

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