8-Queens algorithm example?
Anybody knows good/concise algorithm example for 8-queens? I googled and did not find any good example. ...
algorithm
Required Working Precision for the BBP Algorithm?
Hello, I'm looking to compute the nth digit of Pi in a low-memory environment. As I don't have decimals available to me, this integer-only BBP algorithm in Python has been a great starting point. I only need to calculate one digit of Pi at a time. How can I determine the lowest I can set D, the "number of digits of working precision"? ...
Average function without overflow exception
.NET Framework 3.5. I'm trying to calculate the average of some pretty large numbers. For instance: using System; using System.Linq; class Program { static void Main(string[] args) { var items = new long[] { long.MaxValue - 100, long.MaxVal...
A data structure based on the R-Tree: creating new child nodes when a node is full, but what if I have a lot of objects at the exact same position?
I realize my title is not very clear, but I am having trouble thinking of a better one. If anyone wants to correct it, please do. I'm developing a data structure for my 2 dimensional game with an infinite universe. The data structure is based on a simple (!) node/leaf system, like the R-Tree. This is the basic concept: you set howmany ...
hi i have question here is pseudo code about sift up and sift down on heaps
i have following pseudo code : void siftup(int n) pre condition n>0 && heap(1,n-1) post heap(1,n) i=n; loop /* invariant: heap(1,n) except perhaps between i and its parent if (i==1) break; p=i/2; if (x[p]<=x[i]) break; swap(p,i); i=p; please help me to write it in real code i have question about loop for exa...
question about siftdown operation on heap
i have following pseudo code which execute siftdown operation on heap array suppose is x void siftdown(int n) pre heap(2,n) && n>=0 post heap(1,n) i=1; loop /*invariant heap(1,n) except perhaps between i and it's (0,1,or 2) children*/ c=2*i; if (c>n) break; // c is left child of i if (c+1)<=n /* c+1 is rigth child...
Sorting a string in array, making it sparsely populated.
For example, say I have string like: duck duck duck duck goose goose goose dog And I want it to be as sparsely populated as possible, say in this case duck goose duck goose dog duck goose duck What sort of algorithm would you recommend? Snippets of code or general pointers would be useful, languages welcome Python, C++ and extra k...
What is the better approach to find if a given set is a perfect subset of a set - If given subset is not sorted?
Hi guys, What is the best approach to find if a given set(unsorted) is a perfect subset of a main set. I got to do some validation in my program where I got to compare the clients request set with the registered internal capability set. I thought of doing by having internal capability set sorted(will not change once registered) and do...
Where can I find information on the D* or D* Lite pathfinding algorithm?
There are links to some papers on D* here, but they're a bit too mathematical for me. Is there any information on D*/D* Lite more geared towards beginners? ...
How do I recursively define a Hash in Ruby from supplied arguments?
This snippet of code populates an @options hash. values is an Array which contains zero or more heterogeneous items. If you invoke populate with arguments that are Hash entries, it uses the value you specify for each entry to assume a default value. def populate(*args) args.each do |a| values = nil if (a.kind_of? Hash) #...
How do bezier handles work?
On Wikipedia I found information about bezier curves and made a function to generate the inbetween points for a bezier polygon. I noticed that Expression Design uses bezier handles. This allows a circle to be made with 4 points each with a bezier handle. I'm just not sure mathematically how this works in relation with the formula for b...
Algorithm for autocomplete?
I am referring to the algorithm that is used to give query suggestions when a user type a search term in google. I am mainly interested in how google algorithm is able to show: 1. Most important results (most likely queries rather than anything that matches) 2. Match substrings 3. Fuzzy matches I know you could use Trie or generalized...
Implementing a "flag as spam/offensive" system
I am looking for a community moderated way of managing/eliminating spam and offensive content. Functionality similar to StackOverflow and many other sites seems like a good way to go. Although I'm sure this could greatly vary based on specific needs, I am curious about the backend mechanism/algorithm --that is, has anyone had success u...
If the n-body problem is chaotic, why isn't it used as a RNG?
I'm probably missing something pretty basic here, but if the n-body problem yields chaotic results (except in specific highly-symmetric conditions), couldn't it be used as a "true" random number generator (with initial pseudo-random seeds for masses and velocities) given its non-deterministic nature? ...
Determining which are the text and graphic regions in an image
I dont know whether should I post this question here or not? But if someone knows it, please answer? What are the algorithms for determining which region in an image is text and which one is graphic? Means how to separate such regions? (figure or diagram) ...
views count calculation
Hi, could you give me idea how to calculate unique views of page? If i will increase counter on each page load it will be no good, otherside storing information of viewed pages in session looks like not ideal solution. ...
Algorithm: how to check intersections of recurring events definitions?
The question comes from MS Outlook calendar behavior. Imagine I have two recurring events (starting from today): "each second Monday" and "every odd date". Is there any way to check intersections and/or find the first intersecting date algorithmically without brute-forcing over each date? Definitions can be made in CRON's notations or...
Refining data stored in SQLite - how to join several contacts?
I'm storing contacts between different elements. I want to eliminate elements of certain type and store new contacts of elements which were interconnected by the eliminated element. Problem background Imagine this problem. You have a water molecule which is in contact with other molecules (if the contact is a hydrogen bond, there can b...
New cryptographic algorithms ?
I was wondering about new trends in cryptography. Which algorithms are new ? Which are improved and which died beacuse of the time that past ? For example EEC ( Elliptic Curve Cryptography ) is quite new approach, but definitly not the only one. Could you name some of them ? ...
Reverse regular expressions to generate data
In one of the StackOverflow Podcasts (the one where guys were discussing data generation for testing DBs -- either #11 or #12), Jeff mentioned something like "reverse regular expressions", which are used exactly for that purpose: given a regex, produce a string which will eventually match said regex. What is the correct term for this wh...