It's that time of week again! For this week's programming challenge, I thought I would focus on data structures.

Goal: Construct a binary tree data structure. It may handle any data type you choose, but you must handle sorting correctly. You must also provide a print function that prints each value in the tree on a new line, and the values must be printed in strictly increasing order.

If you're unfamiliar with this data structure, it's a structure that starts with a single "root" node, and this root can have a left child, right child, both, or neither. Each of these child nodes is exactly the same as the root node, except the root has no parent. This branching structure is why it's called a tree. Furthermore, left descendants always have values smaller than the parent, and right descendants always have larger values.

Markov Chains are a stochastic model describing a sequence of possible events in which the probability of each event depends only on the state attained in the previous event. By analyzing a document in some way and producing a model it’s possible to use this model to generate sentences.

For example, let’s consider this quote:

Be who you are and say what you feel, because those who mind don't matter, and those who matter don't mind.

Let’s start with a seed of be, which there is only one of in this text and it’s following word is who. Thus, a 100% chance of the next state being who. From who, there are several next states: you, mind, and matter. Since there are 3 options to choose from, the next state has a 1/3 probability of each. It’s important that if there were for example two instances of who you then you would have a 2/4 probability of next state. Generate a random number and choose the next state, perhaps mind and continue until reaching a full stop. The string of states we reached is then printed and we have a complete sentence (albeit almost certainly gibberish).

Note: if we were in the state mind, our next two options would be . or don’t, in which if we hit . we would end the generation. (or not, up to you how you handle this!)

To take it a step further, you could also consider choosing the number of words to consider a state. For example, two words instead of one: those who has two possible next states: who matter or who mind. By using much longer strings of words for our states we can get more natural text but will need much more volume to get unique sentences.

This programming challenge is for you to create a Markov Chain and Text Generator in your language of choice. The input being a source document of anything you like (fun things include your favourite book, a famous person’s tweets, datasets of reddit / tildes comments), and possibly a seed. The output being a sentence generated using the Markov Chain.

Bonus points for:

• Try it a bunch of times on different sources and tell us the best generated sentences
• Using longer strings of words for the state, or even having it be variable based on input
• Not requiring a seed as an input, instead implementing that into your Markov Chain (careful as infinite loops can occur without considering the seed)
• Implement saving the Markov Chain itself, as it can take very long to generate with huge documents
• Particularly Fast, efficient, short or unique methods

Good luck!

P.S A great place to find many large plain text documents for you to play with is Project Gutenberg.

This problem is based on the Project Euler problem here.

Goal: Given some input describing a triangle of numbers, find the path starting from the top-most row of the triangle and ending at the bottom-most row of the triangle that contains the largest sum of all of the numbers along the path. You may only move downward and you must select an adjacent position to move to. Efficiency is not a requirement for completion.

Constraints:

• The first line of input for a triangle will be a single integer telling you how many rows the triangle will have.
• Each following line of input will be the next row of the number triangle, starting at the first row.
• For each line describing the number triangle, the individual numbers will be separated by a single space.

Note: The constraints above are to keep hard-coded triangles out of submitted solutions while also ensuring that all languages can equally handle this problem without annoying workarounds for lower-level languages. The consistency also makes it easier for beginners to review and understand someone else's code, and makes it easier to receive help if you get stuck. They're not necessarily required, but are highly encouraged.

Example input:

4
1
3 2
4 5 6
7 8 9 10

Corresponding triangle:

   1
  3 2
 4 5 6
7 8 9 10

Expected result: 19 (1 + 2 + 6 + 10)

Extra Credit: As noted on the Project Euler page, you can solve this using a brute force method, but it's incredibly inefficient. Specifically, a brute force solution would be O(2ⁿ) time (exponential). There exists a solution that can be solved in O(n²) time (quadratic). Find this solution.

I have to do an assignment for university soon-ish, and it requires Angular. I'm not very fond of that framework specifically, but I would be interested in making it more interesting as a learning project. I've also recently discovered PureScript, which I have no experience with right now.

Searching online, I've purescript-angular, which hasn't been updated in years. I also couldn't find much else. Of course, I may be missing something simple (for instance, it's actually supported by default in Angular these days), so I wanted to ask if any of you know if this is possible, and if so, how?

Hey all,
I've been studying Common Lisp recently, and as far as I can see, this is a pretty capable, mature language. Moreover, Lisp has been around since the 60s and it doesn't see much usage (as far as I'm aware) outside of Emacs Lisp and AutoLISP. What gives?

Everyone has their own way of visualizing a problem they're working on, and every strategy has some reason for being used. Some people prefer text (e.g. pseudocode) while others prefer diagrams, for example. What do you use to make problems easier to approach, conceptualize, and solve? Why that particular strategy rather than some other one? What kind of practical implementations of your strategy exemplifies the benefits of your strategy for modeling the problem?

What are some of your favorite videos that explain deep topics in depth?

I've recently been on a 3blue1brown binge (youtube) and am looking for more videos of that ilk. Doesn't have to be a series or a consistent uploader, one off videos are sometimes the best. Just thought I'd ask ~comp if there's anything in particular that comes to mind.

This is in part inspired by the video posted by /u/Deimos in the Technical Goals section of Tildes, titled Simplicity Matters

Disclaimer: I'm a novice and this is a half baked idea

Recap

The Caesar cipher is fairly straight forward as it just shifts letters along by a set amount. This means that it's quite easy to brute force. There's only 25 offsets, after all. Try to decode this to see what i mean:

Plqfh 3 foryhv ri jduolf, dqg frpelqh lq d vpdoo erzo zlwk pdbrqqdlvh, dqfkrylhv, 2 wdeohvsrrqv ri wkh Sduphvdq fkhhvh, Zrufhvwhuvkluh vdxfh, pxvwdug dqg ohprq mxlfh. Vhdvrq wr wdvwh zlwk vdow dqg eodfn shsshu. Uhiuljhudwh xqwlo uhdgb wr xvh. Khdw rlo lq d odujh iublqj sdq ryhu phglxp khdw. Fxw wkh uhpdlqlqj 3 foryhv ri jduolf lqwr txduwhuv, dqg dgg wr krw rlo. Frrn dqg vwlu xqwlo eurzq, dqg wkhq uhpryh jduolf iurp sdq. Dgg euhdg fxehv wr wkh krw rlo. Frrn, wxuqlqj iuhtxhqwob, xqwlo oljkwob eurzqhg. Uhpryh euhdg fxehv iurp rlo, dqg vhdvrq zlwk vdow dqg shsshu. Sodfh ohwwxfh lq d odujh erzo. Wrvv zlwk guhvvlqj, uhpdlqlqj Sduphvdq fkhhvh, dqg vhdvrqhg euhdg fxehv.
bonus points for a program that takes the above text and outputs the shift I used without any human input

My dumb idea (didn't work, my bad. They're in normal Caeser cipher now)

I like the simplicity of the shifting characters but having it always be in one direction, and always being the same offset makes it easy to notice the pattern and decode.

If we have the shift value determined by the length of the current word, and the direction of it dependent on if it's a vowel or a consonant.
a pirate is nothing without his ship becomes
b jolgnk kq gvmapgz ppmavbm elp odml so we still have a visibly Caesar-y cipher, but we'll know it's not a true Caesar cipher.
The offset changes for every word and then is applied based on each letter in the word. If it's a vowel, then the encoded value is shifted upwards but if not, it slides down.

For the purposes of the below tomfoolery; prime numbers are consonants and the rest are vowels.

A Valley Without Wind 1 and 2 Steam Key:
B qjsbuf jt opuijoh xjuipvu ijt tijq
FWR0H-GQM7B-5344H

Aces Wild: Manic Brawling Action:
C rktcvg ku pqvjkpi ykvjqwv jku ujkr
K5R0H-29NPM-A3OTE

Age of Empires Legacy Bundle:
D sludwh lv qrwklqj zlwkrxw klv vkls
69PQW-UY3H7-7SQWT

AI War + 4 DLC packs & Tidalis Steam Key:
E tmvexi mw rsxlmrk amxlsyx lmw wlmt
KO99D-73JZ2-XNIK3

AI War: Vengeance Steam Key:
F unwfyj nx stymnsl bnymtzy mnx xmnu
7M2I8-I99N9-6E9F2

Alan Wake Collector's Edition Steam Key:
G voxgzk oy tuznotm coznuaz noy ynov
6ZNJ5-BIVFN-6ZSDZ

Alan Wake's American Nightmare Steam Key:
H wpyhal pz uvaopun dpaovba opz zopw
7RERD-4ACYN-TCDQ2

Amnesia: Dark Descent Steam Key:
I xqzibm qa vwbpqvo eqbpwcb pqa apqx
VGEO8-OU48X-MU7BL

Anachronox:
J yrajcn rb wxcqrwp frcqxdc qrb bqry
3589L-YGF9V-NKGW0

Anodyne:
K zsbkdo sc xydrsxq gsdryed rsc crsz
9HW7H-7Z73Z-6302D

Anomaly Defenders:
L atclep td yzestyr hteszfe std dsta
ICPIB-M63TI-9Y96V

Anomaly Korea:
M budmfq ue zaftuzs iuftagf tue etub
QMPZ2-JUK8B-JRK3V

Anomaly Korea:
N cvengr vf abguvat jvgubhg uvf fuvc
30R9T-C02AA-7DQLG

Anomaly Warzone Earth:
O dwfohs wg bchvwbu kwhvcih vwg gvwd
38UM9-Z26PH-Q4VAU

Anomaly Warzone Earth Mobile Campaign:
P exgpit xh cdiwxcv lxiwdji wxh hwxe
54TYN-AU26Q-5AGGY

Aquaria Steam key:
Q fyhqju yi dejxydw myjxekj xyi ixyf
3853A-YSB4J-6243A

Awesomenauts:
R gzirkv zj efkyzex nzkyflk yzj jyzg
DH9T5-BWOQC-KB6TB

Awesomenauts:
S hajslw ak fglzafy oalzgml zak kzah
RNRJ0-CPT4O-S9UHE

Awesomenauts Cluck Costume:
T ibktmx bl ghmabgz pbmahnm abl labi
VOWWW-QTR3Q-EAS9J

These are encoded using a Caeser shift. The line under the title is a fixed phrase (a pirate is nothing without his ship) for aid in the bonus points

I can post my code if it turns out to be unsolvable (like a bug https://trinket.io/python/dabf2b61f9), but if not; I can also keep going from letters A to Y (sans U) over the weeks with my humble bundle reserves (plaintext or not). I've had these keys for far too long and I'm never going to actually use them, but I also noticed a surge of keys being donated here so figured I might as well change it up.

Have fun

One big thing that has made maintenance of my older code easier has been considering the concept of cyclomatic complexity. In particular, limiting conditional checks to exceptional cases as much as is reasonable has made it easier to focus on the "happy" path of code execution and easily track down the errors, and the limited nesting depth has made things easier to read as well. Overall, my code remains relatively flat and I'm not branching through layers of logic trying to track down a simple bug.

What are some simple things you do to keep your code from being a massive headache long-term?

-> Nim notes <-

Some background

I am learning a new programming language Nim. As many would do, I also take my own notes as I am learning it, running little example by myself, etc.

    .. but I doing that a bit differently.

• I take notes in Emacs Org mode. Org mode has a feature set called Org Babel. That allows one to document the code snippets, and also run them directly in that document, and insert their output results below them -- Notes in Org

  This also helps me document regression of the language behavior between different Nim versions of any, as the exact outputs are documented too. After each major Nim update, I press a single binding (C-v C-v b) in Emacs, and all the output blocks get recalculated.

• But not everyone uses Emacs and Org mode. So to be able to share them to a wider audience, I need to export (Org term) that to a format like HTML, PDF, or Markdown..

• Hugo is a really fast static site generator that uses Markdown as one of the primary content formats. It parses that to HTML using a Go Markdown library called Blackfriday.

• As my notes are in Org mode, and converting them to HTML via Hugo needs them to be in Blackfriday compatible Markdown (which is almost like GitHub flavored Markdown), I starting working on an Emacs Org mode package ox-hugo about a year back. Using that, this Markdown file is generated. Hugo natively supports a subset of Org, but I needed to write this package to use the full power of Org mode.

• Hugo then takes that Markdown and generates the final Nim notes page in HTML.

In the end, I have something that ties together all things of my interest: Nim, Emacs, Org mode and Hugo :)