Algorithms

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Re: Encoding vs Encrypting CPallini13-Jul-07 2:57 CPallini 13-Jul-07 2:57  Encoding a string has to do with its internal representation. For instance, UTF8 or UNICODE maybe different internal representations of the same string. On the other hand, encryption aims to alter the string in such way that its original content is not recognizable by unauthorized people. Usually encryption imply encoding, usually encoding doens't imply encryption. If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile. Re: Encoding vs Encrypting Luc Pattyn13-Jul-07 10:25 Luc Pattyn 13-Jul-07 10:25  Hi, encoding is the process of mapping a collection of some type1 onto a collection of some type2, for instance you can encode the days of the week into the numbers 1 to 7; and the ASCII character encoding maps the character set we all know to a subset of 8-bit numbers. So it is a representation thing (a one-to-one mapping), often aiming at increasing readability or efficiency. encryption is the process of changing the representation in order to hide the content. the goal is not to make things easier, smaller, more economical; it is to hide the true meaning of things. Luc Pattyn try { [Search CP Articles] [Search CP Forums] [Forum Guidelines] [My Articles] } catch { [Google] } Re: Encoding vs Encrypting MarkB77716-Jul-07 23:16 MarkB777 16-Jul-07 23:16  Wikipedia man!!! Mark Re: Encoding vs Encrypting Sathesh Sakthivel18-Jul-07 0:14 Sathesh Sakthivel 18-Jul-07 0:14  Encrypting a file means that one is altering it in order to conceal its contents. Encoding it means one is altering it because of technical reasons related to transmitting it (e.g., the Morse code). Regards, Satips. Don't walk in front of me, I may not follow; Don't walk behind me, I may not lead; Walk beside me, and just be my friend. - Albert Camus Newton Rapheson [modified] devvvy12-Jul-07 15:15 devvvy 12-Jul-07 15:15  Newton Rapheson ring a bell (Goal Seek function from Excel, that's the Algo they used)? Packaged bug free code anyone? Thanks a bunch. Re: Newton Rapheson cp987612-Jul-07 20:37 cp9876 12-Jul-07 20:37  You give no hint of what language you want, maybe Numerical Recipes is a good place to start - here is the 'c' version: Newton-Raphson Method[^] Peter "Until the invention of the computer, the machine gun was the device that enabled humans to make the most mistakes in the smallest amount of time." Re: Newton Rapheson devvvy13-Jul-07 1:27 devvvy 13-Jul-07 1:27  right! Numerical Recipes! Left school for sometime totally forget about it! Minimal Primes Bassam Abdul-Baki11-Jul-07 2:59 Bassam Abdul-Baki 11-Jul-07 2:59  Excellent read.[^] The PostScript file (year 2000) is more informative. "This perpetual motion machine she made is a joke. It just keeps going faster and faster. Lisa, get in here! In this house, we obey the laws of thermodynamics!" - Homer Simpson Web - Blog - RSS - Math - LinkedIn - BM Re: Minimal Primes Paul Conrad12-Jul-07 7:43 Paul Conrad 12-Jul-07 7:43  "Real programmers just throw a bunch of 1s and 0s at the computer to see what sticks" - Pete O'Hanlon Re: Minimal Primes Sathesh Sakthivel18-Jul-07 0:15 Sathesh Sakthivel 18-Jul-07 0:15  Regards, Satips. Don't walk in front of me, I may not follow; Don't walk behind me, I may not lead; Walk beside me, and just be my friend. - Albert Camus Re: Minimal Primes Russell'3-Aug-07 4:29 Russell' 3-Aug-07 4:29  Great Russell Interpolating Elevations Kyudos10-Jul-07 15:48 Kyudos 10-Jul-07 15:48  I have a set of X-Y-Z coordinate points defining a 3D space (actually contour data). Then supposing I want to find the elevation at point X-Y, would the following method work (or does anyone have any other, better, suggestions): 1) Flatten the XYZ data (i.e., take the X and Y coords) 2) Construct the 2D Delauney triangulation for the data set. 3) Find the triangle in which the point X-Y lies. 4) Use the XYZ coords of the vertices of the triangle to interpolate the elevation at XY. Of course the hard part is 3, but is the principle sound? Anyone know of any sample code I can refer to? (bearing in mind I'm not a mathematician or geometrician!) Cheers Re: Interpolating Elevations cp987611-Jul-07 20:43 cp9876 11-Jul-07 20:43  Years ago when I did some work in this area we had data on a rectangular grid - made things easy If you google on "gis interpolation" there are a lot of interesting hits, Peter "Until the invention of the computer, the machine gun was the device that enabled humans to make the most mistakes in the smallest amount of time." String - retrieving the first four jon-809-Jul-07 23:46 jon-80 9-Jul-07 23:46  I need to retrieve the first four alphanumeric characters from a string, basically, if I have "DE WINTER", I need to skip the third character and write "DEWI". Other than going through each substring is there some algorithm for this pattern? Jon Re: String - retrieving the first four CPallini10-Jul-07 0:26 CPallini 10-Jul-07 0:26  It actually depends on the language you're using: string objects usually offer a suitable Replace method. If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile. Re: String - retrieving the first four jon-8010-Jul-07 3:28 jon-80 10-Jul-07 3:28  I'm using JavaScript. Taking this point of view, the problem is that I need to iterate through each character in the source string and replace non-alphanumeric characters with a blank string (''). Jon Re: String - retrieving the first four CPallini10-Jul-07 3:58 CPallini 10-Jul-07 3:58  This http://www.w3schools.com/jsref/jsref_replace.asp[^]] doesn't help you, does it? If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile. Steganography algorithms?? Software_Specialist9-Jul-07 1:56 Software_Specialist 9-Jul-07 1:56  Hiya i am looking for algorithm for Steganography in .mp3 and .jpg.... I found few links while searching in google but all say something different...So any one here with a good algorithm for this task... And yeh i want to implement it in C#.Net..Yeh i know there are many articles for stego in this site but they are not for .jpg or .mp3.. thanks Re: Steganography algorithms?? Luc Pattyn9-Jul-07 2:30 Luc Pattyn 9-Jul-07 2:30  Search CodeProject for it, you will find several articles. And yes there are many ways to do it. Luc Pattyn try { [Search CP Articles] [Search CP Forums] [Forum Guidelines] [My Articles] } catch { [Google] } Re: Steganography algorithms?? Software_Specialist9-Jul-07 2:42 Software_Specialist 9-Jul-07 2:42  I dont think there is any article for .mp3 and .jpg in code project...Thats what i mentioned in my post... Yeah there could be many ways, just trying to know which algo is the best way if somebody has already achieved that... anywayz... Thanks Re: Steganography algorithms?? Luc Pattyn9-Jul-07 3:01 Luc Pattyn 9-Jul-07 3:01  I dont know for mp3, I have seen several for JPEG. Luc Pattyn try { [Search CP Articles] [Search CP Forums] [Forum Guidelines] [My Articles] } catch { [Google] } Re: Steganography algorithms?? Vasudevan Deepak Kumar17-Jul-07 6:45 Vasudevan Deepak Kumar 17-Jul-07 6:45  http://en.wikipedia.org/wiki/Steganography[^] Vasudevan Deepak Kumar Personal Homepage Tech Gossips linear algebra library ovoundaga8-Jul-07 2:03 ovoundaga 8-Jul-07 2:03  hi !i am writting a project where i have to deal with a lot of matrices and still a biginner in programming.i want to know if there is a library for linear algebra in c and where to get it.thanks!! Re: linear algebra library Stephen Hewitt8-Jul-07 15:03 Stephen Hewitt 8-Jul-07 15:03  If you're using C++ I'd go for Boost's uBLAS[^] library. If you are going to use C try the BLAS[^] library. Steve Re: I think this shouldn't be here... p_v_chaitanya2-Jul-07 1:51 p_v_chaitanya 2-Jul-07 1:51  Sure Sir, gonna delete this right away..... Am a newbie here and wanted to know more on Software Architecture with feedbacks and comments on topic I have raised at my blog pchaitanya.wordpress.com..... Any feedback would be highly appreciated.... Thanks, Chaitanya Chaitanya

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