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  Find the kth smallest number in an array

This is an classical question, the general solution to this question is first using sorting algorithm to sort the array, then get the kth number in the array, the complexity is O(nlogn), we can also use selective sort or head sort to, the complexity of selective sort is O(kn) and heap sort is O(nlogk). The better solution is to use quick sort to find the kth smallest number, the complexity is O(n), the worst case cost is O(n^2). But today we introduce one more solution which has the worst case c...

   Sort, Quick sort, Search,Smallest     2013-01-09 06:20:54

  Use pdb to help understand python program

  As I have mentioned in Why do I need a debugger?: (3) Debugger is a good tool to help you understand code. So when I come across difficulty to understand vfscount.py code in bcc project, I know it is time to resort to pdb, python's debugger, to help me. The thing which confuses me is here: counts = b.get_table("counts") for k, v in sorted(counts.items(), key=lambda counts: counts[1].value): print("%-16x %-26s %8d" % (k.ip, b.ksym(k.ip), v.val...

       2017-08-22 22:42:37

  How to find which process a file is being written by in Linux?

Some people ask a file is being written by one process and they want to check this process, but they cannot find the process even with sof. This question is very common and there are many solutions, here we introduce a straightforward method. In Linux, each file will be stored on one device and of course there will be a relative inode, then we can use vfs.write to know who is writing the inode on one specified device continuously. Luckily there is inodewatch.stp in the installation package of s...

   Linux,process,file write     2013-03-16 21:44:35

  20 bit operations programmers should know

While talking about bit operation, programmers usually think about its efficiency. In embedded programming and system core optimization, appropriate use of bit operations is always a fascinating. When finding a job, it will help you a lot if you use bit operations when writing codes. Mastering simple bit arithmetic skills is necessary. 1. Get maximum int value int getMaxInt(){           return (1 << 31) - 1;//...

   Bit operation, Tips     2012-12-19 12:53:33

  Use cases of Java enumeration

JDK 1.5 introduces a new type -- enumeration. In Java, it's just a small feature, but it can bring us much convenience.Here we summarize some use cases of Java enumeration. 1. Constant Prior to JDK 1.5, we can define constant as public static final..., now we can use enumeration to group all constants in one enum variable and it also provides some useful functions. public enum Color {     RED, GREEN, BLANK, YELLOW   }  2.In Swit...

   Java, Enum,enumeration     2013-01-05 09:15:30

  Speech balloon with pure CSS--One step further

Many of us want to add cool features to our websites to make our websites user friendly ad more attractive. Especially in Web2.0 era. Today we are talking about adding speech balloon feature to our webpage so that we can display beautiful help windows while users mouse over some help icons on our page. First, let me introduce one post written by Umar Ashfaq named "How to create a speech balloon with pure CSS". He also explains how this works. You can also refer Magic CSS shape for more informati...

   Speech balloon, Pure CSS,border     2013-03-16 04:11:58

  TIOBE: PHP is coming back

TIOBE released the programming language index for July 2013. The highlight of this month is that PHP is coming back. It ranks the fifth and has an increase of 1.54% compared to January. There are no changes in the ranking for the top 4 languages. The reason why PHP is back may be attributed to the new PHP Zend Framework that was released in September 2012, but this reason is not very convincing. PositionJul 2013PositionJul 2012Delta in PositionProgramming LanguageRatingsJul 2013Delta Jul...

   TIOBE,PHP,Zend framework,July     2013-07-09 05:22:50

  Big file transfer in Linux

It's very common that we need to transfer files between two different hosts such as backups. It is also an very simple task, we can use scp or rsync to complete the task well. But what if the file is very big, it may take some time to transfer it. How can we transfer a big file with high speed? Here we propose one solution. Copy file If we copy one uncompressed file, then we should follow below steps: Compress data Send it to another host Uncompress the data Verify the data integrity This will...

   Linux, SCP,ZIP     2013-01-10 05:55:50

  Uber’s audio recording plan in Brazil and Mexico

Uber has recently come out with a plan to introduce a new feature to its App in Brazil and Mexico. The feature will record the conversations between the driver and the passenger, with their consent. But consent here is a bit tricky. Basically, if the driver decides to turn on the recording feature, they are not obligated to warn the passenger and vice versa. Once the recording has been made and submitted to support for some kind of violation, neither of the two parties will have the ability...

   UBER,SECURITY,PRIVACY,VOICE RECORDING APP,NEW FEATURE     2019-11-21 09:20:36

  Significance and use of do{...}while(0)

In some Linux kernel and other open source codes, we can see some codes like below: do{ ... }while(0) This code snippet is not a loop, it seems there is no significance of using do...while this way, then why should we use it? In fact, the significance of do{...}while(0) is better than optimizing your code. After some research, we summarize some benefits of it. 1. Help define complex macro to avoid error #define DOSOMETHING()\ foo1();\ foo2(); The me...

   do{...}while(0), optimization     2012-10-21 21:13:22

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