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  Java Cipher encryption/decryption example

In Java, Cipher is the API for doing data encryption/decryption. Many cryptographic algorithms such as AES, DES, RC4 etc can be specified when creating Cipher instance. The Cipher instance calls the underlying algorithm specific implementation to do the actual encryption/decryption.  Before doing the encryption/decryption, a key needs to be created and it will be used to do the encryption/decryption. A sample program for performing all these is : import java.security.Key; import javax.cryp...

   Java, Java Security, Cipher, Example, Sample     2015-08-14 07:07:10

  The faster-than-fast Fourier transform

The Fourier transform is one of the most fundamental concepts in the information sciences. It’s a method for representing an irregular signal — such as the voltage fluctuations in the wire that connects an MP3 player to a loudspeaker — as a combination of pure frequencies. It’s universal in signal processing, but it can also be used to compress image and audio files, solve differential equations and price stock options, among other things.The reason the Fourier...

   FFT,Fast fourier transform,MIT,Compression     2012-01-19 09:59:09

  Some thoughts about competitive programming

Many programmers may have experience in participating different kinds of coding competition while they are in college. Many of them are hired by top IT companies for their excellent performance during these kinds of coding competitions. There are some famous competitions organized by IT companies such as Google Code Jam, Facebook hackathons etc. Coding competitions are places where programmers can show their talents in programming and the skills they have. Usually programmers will solve some to...

   Coding,competition     2014-03-02 07:26:21

  Generate first N prime numbers

Recently I am taking an online course named "Startup Engineering" on coursera. There is one assignment which is to use NodeJS to write a program to generate the first 100 prime numbers. This may be very easy for many people. Here I just want to share with you the code to generate not only the first 100 prime numbers. but also any number of prime numbers. Below is the code snippet: //Helper class to generate prime numbers var PrimeProcessor=(function(){ var primeArray=[]; functio...

   Algorithm,Prime number,NodeJS,coursera,JavaScript     2013-06-29 22:08:22

  Algorithm: Traverse binary tree

Preface There are three ways to traverse a binary tree based on the traversing order. Pre-Order: Root - Left - Right In-Order: Left - Root - Right Post-Order: Left - Right - Root Take below binary tree as example The node to be traversed in different order would be Pre-Order: A - B - C - D - E - F In-Order: C - B - D - A - E - F Post-Order: C - D - B - F - E - A Below are the implementations of different orders for traversing the binary tree. Pre-Order Traversing Recursive implementation N...

   ALGORITHM,BINARY TREE     2019-03-01 22:49:04

  Computer skills one can learn within one day

Computer related technical skills are usually thought as complicated and difficult to understand. It's very difficult for one to get hands on one skill or master one skill. But if you really do want to learn something useful within one day, there are some good choices which will not take too long to get to know and use.. Version control:- Git, GitHub and SVN Regular expressions AWK sed Grep Learn how to do things with Vim that you never knew could be done. Set up a crawler that can scrape some ...

   Computer skills,Learn     2013-09-16 08:51:35

  Gaussian Blur Algorithm

Usually, image processing software will provide blur filter to make images blur. There are many algorithms to implement blur, one of them is called Gaussian Blur Algorithm. It utilizes Gaussian distribution to process images. This article is to introduce Gaussian Blur algorithm, you will find this is a simple algorithm. In fact, it is a kind of data smoothing which can be used in many situations. 1. Gaussian Blur theory The so called blur can be understood as taking a pixel as the average valu...

   ALGORITHM,GAUSSIAN BLUR, IMAGE BLUR     2020-09-12 02:34:40

  Fuzzy search algorithm in Sublime Text

Fuzzy string searching is the technique of finding strings that match a pattern approximately (rather than exactly. In many editors, we can easily find the Find menu item to do exact matching. While in Sublime Text and some other editors, we can use fuzzy string searching as well if we just want to have an approximate match. There is some algorithm implemented in Sublime Text to implement achieve this. First the search query is split into characters, join them with a regex wildcard, and then run...

   Sublime Text,Fuzzy search     2013-10-14 22:49:38

  Generate certificate with cRLDistributionPoints extension using OpenSSL

In an X509 certificate, the cRLDistributionPoints extension provides a mechanism for the certificate validator to retrieve a CRL(Certificate Revocation List) which can be used to verify whether the given certificate is revoked.   A cRLDistributionPoints extension can contain one or more DistributionPoints where the CRL can be retrieved from. Each DistributionPoint consists of three fields,each of which is optional: distributionPoint : it contains either a SEQUENCE of general...

   X509,OPENSSL,CERTIFICATE,CRLDISTRIBUTIONPOINT,EXTENSION     2015-10-22 03:41:11

  The significance of coding competition to actual work

Some friends asked this question: In secondary schools we participate in the NOI, in university we participate in ACM/ICPC, TopCoder.What's the significance of coding competition to actual work? I participated in the NOI from 1994 to 1996, ACM/ICPC from 1999 to 2000 and TopCoder in 2002 for six months. Later I paid little attention to coding competition, so I may not understand the changes in recent years and race mode . The capabilities we can get by participating the competition can be summari...

   ACM,Programming,Facebook,TopCoder     2013-02-28 20:38:23

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