With the Code Jam 2013 qualification starting soon, I decided to look at one of the past rounds. With 2011 I found one, in which I did not put too much time and effort in.
Candy Splitting. If you’re unfamiliar with the puzzle, read the problem first.
I managed to solve the the small input set, but couldn’t compute the large one in time. This usually indicates an issues with the chosen complexity to solve the puzzle, so let’s start evaluation where it went wrong.
Even though there are libraries and tools to concatenate two canonical wave files, here is how you can do it manually, just in case you need to or are interested.
Take one of the files and add the second files minus the header. Then modify sizes of the file and the actual data part.
You might want to look at the definition of a wave file first.
united-coders.com is not that big. We’re currently getting in between 500 and 1000 unique visits a day. As we’re coders we like to host ourselves. We’ve previously been on a real root server, which was a bit overkill. So we decided try something smaller and cheaper and we’re currently hosting this site for around $7 per month with enough headroom for more traffic. We do have the occasional spike in the 5000 range when we publish something that catches on. So this needs to be covered.
If you’re interested in the setup and a detailed description, you can find it on RichWP.
A virtual server is a slice of a real server with a certain amount of resources dedicated to you. For us (speaking united-coders.com), the smallest version is sufficient. We got one cpu share (hard to measure, yeah) and a guaranteed 1GB of RAM (up to 2GB dynamically, but we only work with what we will constantly have).
The united-coders.com blog migration was my motivation to update a non-technical, german blog from a serendipity blog (short s9y) base to wordpress. The reason of switching to wordpress are different and will be reported here only from the technical view: Regularly updates, many themes and an active development community – but php.
First step for a blog migration (content and hosting) is a clean new installation on the target host. Use a dummy domain (and not a sub-folder) and configure a theme and some necessary plugins.
This is a small “disaster” summary on how one small mistake in an email setup lead to a company wide email outage and several entries on spam lists.
Consider the following scenario: small company, few imap accounts, one domain (we call worksfine.com) and one catchall/forward domain (we call fluky.com).
Some day, fluky.com is down again, so the forwards are temporarily not working. Terrified by that, the company calls another “admin”, as the usual guy is on vacation or otherwise unavailable.
The admin sees the problem in the imap accounts, which are tied to worksfine.com, not the real reason that fluky.com forwards are currently simply not forwarding. So he switches the accounts on a few computers from imap to pop3 (fetch and delete from server). Of course the problem persists, but magically vanishes after a while. Yeah, you guessed it, fluky.com is up again and delivering the mails which accumulated during the downtime.
Now comes the interesting part. On of the workers on a changed workstation sends an email, with a 10mb attachement. The workstation is using a nice MS product, sends the mail fine but fails to move it to the sent folder and puts it back into the send queue for a retry. I cannot exactly explain why this has happened, as I did not yet have time to inspect the machine. From what I know I guess, that the sent folder was still the imap account, but the mail server addresses for pop are different so the ssl certificates did not match and the move failed. Or some even simpler reason. ( insert Murphy’s Law here)
Luckily, that email was addressed to the whole company and a handful of customers. So after a few minutes the DOS “attack” on the own company was successful. Also a few customers were slightly upset and the address did end up on the blacklist filters on mail appliances and mail providers used by the customers.
This is the first part of a story on how we tried to migrate from Drupal 6.
There’s nothing inherently wrong with drupal, but our version 6 installation was getting a bit dusty and had way more features that we needed. We wanted to move to something simpler, cheaper, faster, more scalable, newer, easier ….
The goal was to live without a server, in the cloud and getting free scalability promised. We’re not, and still are not, getting hit very hard and the ocasional spike was no real issue on our Drupal setup or our server. But it was time for some change.
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Google Code Jam 2012 started this weekend and this years qualification round was simpler than other years.
The first exercise is a character mapping problem. You will get some gibberish input and have to encode it to normal english sentences.
gibberish: ejp mysljylc kd kxveddknmc re jsicpdrysi ready: our language is impossible to understand
And there was only the small data set (with many tries to solve it) available. Ok, looks like a classical problem and I start thinking to build a solution with counting common english characters or iterate over all permutation to find words (from an english dictionary).
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The first round of the facebook hackercup 2012 had three problems. All problems have to be solved in 24 hours and coders with three successful solved entries goes to round 2.
The problem “Recover the Sequence” can be solved in two lines of code (+ some lines for input and output).
Merge sort is one of the classic sorting algorithms. Conceptually, a merge sort works as follows. Divide the unsorted list into n sublists (n is 2 in the example), each containing 1 element (a list of 1 element is considered sorted). Repeatedly Merge sublists to produce new sublists until there is only 1 sublist remaining. (This will be the sorted list.)
The problem description starts with the pseudo code – I translated into a python class.
The second problem from this year facebook hackercup sound like the classic knapsack problem. But the solution is much easier (words are in fixed sort order). Feel free to find a smarter algorithm or comment my python solution.
We are starting preparations for Hacker Cup 2013 really early. Our first step is to prepare billboards to advertise the contest. We have text for hundreds of billboards, but we need your help to design them.
The billboards are of different sizes, but are all rectangular. The billboard widths and heights are all integers. We will supply you with the size in inches and the text we want printed. We want you to tell us how large we can print the text, such that it fits on the billboard without splitting any words across lines. Since this is to attract hackers like yourself, we will use a monospace font, meaning that all characters are of the same width (e.g.. ‘l’ and ‘m’ take up the same horizontal space, as do space characters). The characters in our font are of equal width and height, and there will be no additional spacing between adjacent characters or adjacent rows. If you print a word on one line and print the next word on the next line, you do not need to print a space between them.
Let’s say we want to print the text “Facebook Hacker Cup 2013″ on a 350×100″ billboard. If we use a font size of 33” per character, then we can print “Facebook” on the first line, “Hacker Cup” on the second and “2013” on the third. The widest of the three lines is “Hacker Cup”, which is 330″ wide. There are three lines, so the total height is 99″. We cannot go any larger.
This year qualification round had three problem. The easy one was Alphabet Soup – classic character counting problem.
Alfredo Spaghetti really likes soup, especially when it contains alphabet pasta. Every day he constructs a sentence from letters, places the letters into a bowl of broth and enjoys delicious alphabet soup.
Today, after constructing the sentence, Alfredo remembered that the Facebook Hacker Cup starts today! Thus, he decided to construct the phrase “HACKERCUP”. As he already added the letters to the broth, he is stuck with the letters he originally selected. Help Alfredo determine how many times he can place the word “HACKERCUP” side-by-side using the letters in his soup.
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