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  Permutation implementation in Java

Permutation is a very basic and important mathematic concept we learned in school. It has very practical applications in real world. For example, in football. In simple, permutation describes all possible ways of doing something. For example, there are six permutations of the set {1,2,3}, namely: (1,2,3), (1,3,2), (2,1,3), (2,3,1), (3,1,2), and (3,2,1). In general, for n items, there are n! number of permutations to arrange these items. How can we implement this algorithm in programming programm...

   Permutation,Implementation,Java,Sample     2015-03-26 02:18:14

  Check file readability in Java

File operation is quite platform dependent. Although Java is a cross platform programming language, the file operation in Java is also platform dependent. The obvious evidence is the file permission check. In Java, we can call canRead(), canWrite() and canExecutable() to check whether the program can read, write or execute the file specified. However, on Windows, when we call canRead() on a File object, we may get unexpected result. Actually, on Windows, when we call canRead() on a File object, ...

   Java,Files,Readable,Check     2013-12-05 06:10:15

  What to put on whiteboard during an interview

As a programmer, you may go through different kinds of programming tests while interviewing for jobs. The most famous and difficult one may be the whiteboard test for lots of people. Usually the interviewer will give the candidate an algorithm problem or case study and ask the candidate to implement the algorithm with his/her favorite programming language. The code to be written is not too much but it requires the candidate to thoroughly consider different edge cases. So wha...

   TIPS,INTERVIEW,WHITEBOARD TEST     2014-08-29 20:34:52

  MySQL Index Merge Optimization Practices

In production environment databases, it is often seen that some SQL where conditions include: equal condition on a normal index + primary key range query + order by limit Although using a normal index would be more efficient, the system chooses to use index merge instead in some cases. This article explores such index merge situations. Index Merge Official Introduction   The Index Merge access method retrieves rows with multiple range scans and merges their results into one. Generall...

   INDEX MERGE,MYSQL,PRIMARY INDEX,SECONDARY INDEX     2024-09-10 04:52:26

  Let 's write some front end codes

I've seen a lot of arguments that there is no much technical value writing web portal, I think that the vast majority of good programmers will try many different things. The low level development and machine learning are not the only technologies which are  full of wisdom and challenges, I wrote web site for a few years, it is difficult to say that this is my initial interest, although I touched on other technologies as well, I still feel building website is challenging. Front end developme...

   Front end development, JavaScript,CSS     2013-01-22 04:00:24

  REST和gRPC对比全知道

长期以来，REST是构建API的唯一“标准”。它取代了混乱的“太多XML”的SOAP。但是近年来，出现了新的替代品。2015 年，Facebook 向公众发布了GraphQL，而 2016 年，Google 推出了gRPC。本文将重点介绍 gRPC，并与仍广泛使用的 REST 进行比较。 概述 以下表格将为您提供讨论点的概述，并显示 REST 和 gRPC 的优劣之处。 主题 REST gRPC 标准化 没有标准 定义明确 范式 基于资源...

   COMPARISON,GRPC,REST     2023-04-29 06:44:09

  JavaScript tips both novice and veteran developers can benefit from

In this post, we will share some less known but powerful JavaScript tips which can benefit both novice and veteran JavaScript developers. 1. Truncate array with array length We all know that object are passed by reference in JavaScript, but we may be bitten by this rule. Please check below example: var arr1 = arr2 = [1, 2, 3]; //Change arr1 arr1 = []; // arr2 will still be [1,2,3] arr1 and arr2 point to the same array [1,2,3] initially, later when arr1 repoints to [], the reference to arr2 is n...

   JavaScript,Array,push     2013-08-21 04:09:10

  A trap about PHP random number

The method to get random number in PHP is very simple, we only need to use rand() function. int rand ( int $min , int $max ) One function call can return the random number in a specified range. But in fact, the random number in computer is actually pseudorandomness, generally to increase the randomness, we may set a random seed before calling rand(). void srand ([ int $seed ] ) According to other language features, we should pass a time value as a parameter to the srand() function, generally...

   PHP,rand,srand,mt_rand     2013-06-07 09:10:10

  Be Careful When Using Cursor to Help Build Application

Below are some tips or tricks when building application with Cursor. These lessons are based on my recent experience while building a Sudoku game (just wanna test Cursor's capability). Do commit frequently. Recommend doing commit for every big change (a new feature such as a new button added for some function, some big UI change like added some new component changing the UI layout a bit) Test everything (regression testing) after doing big change. It may affect existing functions when adding n...

   TIPS,AI,GUIDE,CURSOR,DRAWBACKS     2025-01-05 03:37:00

  Python Process Protection Watchdog

Project Design Purpose: During participating the cyber exercise as red team member, we found that the injected malware or attack launching program can easy be stopped by the blue team or defense program / mechanisms via killing the process / deleting the file. To address this, our project aims to develop a robust watchdog program designed to bind to target programs, diligently monitor their execution states, and ensure uninterrupted functionality. Continuous Monitoring: Establish a vigilant wa...

       2024-09-14 11:09:14

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