Hey there,

I wanted to know which sets of passports grant together visa-free access to every country in the world, but I could not easily find that info online. So I figured that I could try to write a small program to determine these sets of passports myself, and then it occurred to me that it would probably be a fun programming challenge to organize, so here we go.

Here's the challenge.

1. Scrape the data you need for instance from The Henley Passport Index.
2. Design a clever algorithm to efficiently find out which are the smallest sets of passports that will grant you visa-free access to every country in the world.
3. Optional. Allow the user to specify which passports they already hold and find out which sets of passports would complement their passports well.
4. Optional. Rank the sets of passports by how easy it is to acquire citizenship in those countries.

The choice of the programming language is yours, bonus points if you write it in assembly 😂

Feel free to collaborate and share your solutions (the algorithms and the actual results) in the comments, and feel free to share your own twists to the challenge that could make it even more fun & interesting.

The person with the most clever, efficient and elegant algorithm wins!

Happy coding folks!

Background: Bitwise operators are operators that perform conditional operations at the binary level. These operators are bitwise AND &, bitwise OR |, bitwise XOR ^, and bitwise NOT ~, not to be confused with their logical operator counterparts, i.e. &&, ||, !=, and ! respectively.

Specifically, these operations take the binary values of the left- and right-hand terms and perform the conditional operation on each matching bit position between both values.

For instance, 3 | 4 takes the binary value 010 from 2 and 100 from 4. From left to right, we compare 0 || 1, 1 || 0, and 0 || 0 to get 110 as the resulting binary. This produces the integer value 6.

Goal: Your challenge is to implement one or more of these bitwise operators without using the native operators provided to you by your language of choice. Logical operators are allowed, however. These operators should work on integer values. These operators will likely take on the form of a function or method that accepts two arguments.

Bonus challenges:

• Implement all of the operators.
• Don't use any native binary conversion utilities.
• Whether or not you implement all operators, write your code in such a way that allows for good code reusability.
• For statically typed languages, handle integers of different types (e.g. int vs. uint).

Edit: Minor correction for the sake of accuracy, courtesy of @teaearlgraycold.

Lox is a toy programming language that is designed in Java and C at craftinginterpreters.com.

My challenge to you is: given the constraints of the Lox language, what are some creative or advanced programs you can create?

This page provides a rundown of the design of Lox.

To kick it off, here's a simple function that estimates the value of pi:

fun estimatePi(rounds) {
	var pi = 0;
	var alt = 1;
	for (var i = 0; i < rounds; i = i + 1) {
		pi = pi + alt * 4/(2 * i + 1);
		alt = -alt;
	}
	return pi;
}

print "The value of pi is:";
print getPi(100000);

It has been a while since the last time we did something like a programming challenge, so here's one for ya.

The life story of the author before you get to the recipe

I've been working on a little "today" website, showing what day it is, if it's a significant date for holiday/independence/... reasons, and one of the things I wanted was a small calendar display that showed the full month and days in each week. Like how XFCE's Clock plugin does it.

So I got to figuring it out and after finishing it up I thought this could be a nice little programming challenge. It has one input (the date) that can be in any of the rows and columns, and it's up to you to figure out all the rest.

Here's how mine looks in about 250ish lines of TypeScript (TSX technically) and SCSS.

The Recipe

Make a mini calendar display that shows all the days of the current month and at least one day of each adjacent month. So for example for May 2023: the 31 days in May, the 30th of April and the 1st of June should at least be visible.

It can be in any language with any method of rendering; simple text, TUI/GUI toolkit, web-based, raytraced in some game engine, nixie tubes, whatever.

Bonus Points

• Highlight the current day name in the first row, if you're including day names.
• Highlight the current day number, wherever it is.
• Highlight the current week row, wherever it is.
• Differentiate the days of current month and the days of the other adjacent months, wherever they are.

Some Tips

Showcase

If at all possible and with at least a few entries I will try to run all the submissions myself and create a little showcase website for it.

This is a bit of a silly challenge that came to mind when I saw a discussion about obfuscating mailto links on the unofficial Discord server. This challenge is intentionally meant to be ridiculous and encourages horrendous solutions that should never see the light of day in actual production code.

Some Background

On the internet, bots are an incredibly common. They may do anything from crawling through webpages to map out valid links on the web, to spamming forums with links to scam websites. Among some of the less ethical uses of bots is the collection of any email addresses that might be sitting around in a webpage's source code, either made visible to the user or hidden behind some alternative text. These bots collect these email addresses for any number of purposes, including phishing attempts to hijack accounts.

Commonly, these emails can be found sitting inside of so-called mailto links, which will open your default mail application and pre-populate the recipient's address, preparing you to send a new email in a single click. It's a safe bet that the vast majority of mailto link implementations aren't very sophisticated, simply providing a snippet that looks much like the following:

<a href="mailto:johnsmith@example.com">Contact Me</a>

Given the above, most bots will likely only ever scrape a webpage for a link containing href="mailto:. A simple form of obfuscation to combat a bot could be to leave the href attribute empty on initial page load, capture the on click event, dump the mailto email address into the href attribute, and finally remove the on click event handler from the link before re-sending the click event.

We're not here for simple, however.

Challenge

As suggested in the title, the challenge is to over-engineer this obfuscation. There is only one hard requirement:

Clicking the "Contact Me" link should, to the user's perception, function (mostly) identically to a simple mailto link. Specifically, clicking the link should ultimately result in the user's mail application opening (or being prompted to open) with no further input from the user and the "to" field being correctly pre-populated with the intended email address. This means that captchas and the like are not allowed. Delays in triggering the mail application due to processing layers of obfuscation, however, are expected and acceptable (although "until well after the heat death of the universe" is not an acceptable delay, so let's be reasonable).

Apart from the requirement above, solutions that require increasingly more sophisticated methods of de-obfuscation for a bot to discover your email address are preferred. The more complicated a bot's design would need to be to discover your email address, and the more painful it is for other programmers to see the abomination you've created, the better.

CSS is not required. A functioning webpage is not required. An entire web server is not required. A full, working web project including a framework with defined routes, security features, a VM provisioning script, and whatever the fuck else you would need is not required. You can build an actual web project around this if you wish, but code snippets and some comments explaining what does what will be more than sufficient.

Hi everyone! It's been a long time since last programming challenge ^list, and here's a nice one I've encountered.

If you search for something like 7km to AU, you'll get your answer. But how is it done? I don't think they hardcoded all 23 units of distance and every conversion factor between them.

If you were programming a conversion system - how would you do it?

First of all, you have input in format that you can specify, for example something like this:

meter kilometer 1000
mile kilometer 1.609344
second minute 60
...

Then you should be able answer queries. For example 7 mile meter should convert 7 miles to meters, which is 11265.41.

Can you design an algorithm that will convert any unit into any other unit?

Edit: Some conversion rates I extracted from wikipedia:

ångström
0.1nm
astronomical unit
149597870700m
attometre
0.000000000000000001m
barleycorn
8.4m
bohr
0.00846
cable length (imperial)
185.3184m
cable length
185.2m
cable length (US)
219.456m
chain (Gunters)
20.11684m
cubit
0.5m
ell
1.143m
fathom
1.8288m
femtometre
0.00000000000001m
fermi
0.00000000000001m
finger
0.022225m
finger (cloth)
0.1143m
foot (Benoit)
0.304799735m
foot (Cape) (H)
0.314858m
foot (Clarke's) (H)
0.3047972654m
foot (Indian) (H)
0.304799514m
foot,metric
0.31622776602m
foot,metric (long)
0.3m
foot,metric (short)
0.30m
foot (International)
0.3048m
foot (Sear's) (H)
0.30479947m
foot (US Survey)
0.304800610
french
0.0003m
furlong
201.168m
hand
0.1016m
inch
0.0254m
league
4828m
light-day
25902068371200m
light-hour
107925284880m
light-minute
17987547480
light-second
299792458m
light-year
31557600light-second
line
0.002116m
link (Gunter's)
0.2011684m
link (Ramsden's; Engineer's)
0.3048m
metre
1m
m
1metre
km
1000m
mickey
0.000127
micrometre
0.000001
mil; thou
0.0000254
mil
10km
mile (geographical)
6082foot (International)
quarter
0.2286m
rod
5.0292m
rope
6.096m
shaku
0.303 0303m
span (H)
0.2286m
stick (H)
0.0508m
toise
1.949 0363m
twip
1.76310
yard
0.9144m

On lobste.rs I found link to an article from Vidar Holen, the author of shellcheck. He made a fork bomb that is really interesting. Here's the bomb:

DO NOT RUN THIS.

eval $(echo "I<RA('1E<W3t`rYWdl&r()(Y29j&r{,3Rl7Ig}&r{,T31wo});r`26<F]F;==" | uudecode)

This may look pretty obvious, but it's harder than you think. I fell for it. ^twice. Can you find out how this bomb works?

Warning: executing the bomb will slow down your computer and will force you to restart.
You can limit impact of the fork bomb by setting FUNCNEST.

export FUNCNEST=3

Have fun!

In an effort to make these weekly, I present a new programming challenge.

The challenge this week is to compress some text using a prefix code. Prefix codes associate each letter with a given bit string, such that no encoded bitstring is the prefix of any other. These bit strings are then concatenated into one long integer which is separated into bytes for ease of reading. These bytes can be represented as hex values as well. The provided prefix encoding is as follows:

Challenge

Your program should accept a lowercase string (including the ~ character), and should output the formatted compressed bit string in binary and hex. Your final byte should be 0 padded so that it has 8 bits as required. For your convenience, here is the above table in a text file for easy read-in.

Example

Here is an example:

$> tildes ~comp
10010100 10010010 01011010 10111001 00000010 11000100 00110000 10100000
94 92 5A B9 02 C4 30 A0

Bonuses

1. Print the data compression ratio for a given compression, assuming the original input was encoded in 8 bit ASCII (one byte per character).
   2. Output the ASCII string corresponding to the encoded byte string in addition to the above outputs.
2. @onyxleopard points out that many bytes won't actually be valid ASCII. Instead, do as they suggested and treat each byte as an ordinal value and print it as if encoded as UTF-8.
3. An input prefixed by 'D' should be interpreted as an already compressed string using this encoding, and should be decompressed (by inverting the above procedure).

Previous Challenges (I am aware of prior existing ones, but it is hard to collect them as they were irregular. Thus I list last week's challenge as 'Week 1')
Week 1

Its been a while since we did one of these, which is a shame.

Create a program that takes is an input of the type: "d6 + 3" or "2d20 - 5", and return a valid roll.
The result should display both the actual rolls as well as the final result. The program should accept any valid roll of the type 'xdx'
Bonuses:

• Multiplication "d6 * 3"
• Division "d12 / 6"
• Polish notation "4d6 * (5d4 - 3)"

As a side note, it would be really cool if weekly programming challenges became a thing

Previous challenges

It's time for another coding challenge!

This challenge isn't mine, it's this challenge (year 5, season 3, challenge 3) by ČVUT FIKS.

The task is to design a network communication protocol. You're sending large amount of bits over the network. The problem is that network is not perfect and the message sometimes arrives corrupted. Design a network protocol, that will guarantee that the decoded message will be exactly same as the message that was encoded.

MESSAGE => (encoding) => message corrupted => (decoding) => MESSAGE

Corruption

Transmitting the message might corrupt it and introduce errors. Each error in a message (there might be more than one error in a single message) will flip all following bits of the message.

Example:

011101 => 011|010

(| is place where an error occured).

There might be more than one error in a message, but there are some rules:

• Minimum distance between two errors in a single message is k

• Number of bits between two errors is always odd number

According to these rules, describe a communication protocol, that will encode a message, and later decode message with errors.

Bonus

• Guarantee your protocol will work always - even when errors are as common as possible

• Try to make the protocol as short as possible.

Hello everyone! It has been a while since last programming challenge, it's time for another one!

This week's goal would be to build your own interpreter.

Interpreter is program that receives input and executes it. For example Python is interpreted language, meaning you are actually writing instructions for the interpreter, which does the magic.

Probably the easiest interpereter to write is Brainfuck interpreter. If someone here doesn't know, Brainfuck is programming language, which contains following instructions: ,.<>[]-+. Other characters are ignored. It has memory in form of array of integers. At the start, pointer that points to one specific memory cell points to cell 0. We can use < to move pointer to left (decrement) and > to move pointer to right (increment). . can be used to print value of cell the pointer is currently pointing to (ascii). , can be used to read one character from stdin and write it to memory. [ is beggining of loop and ] is end of loop. Loops can be nested. Loop is terminated when we reach ] character and current value in memory is equal to 0. - can be used to decrement value in memory by 1 and + can be used to increment value in memory by 1. Here's Hello World:

++++++++++[>+++++++>++++++++++>+++>+<<<<
-]>++.>+.+++++++..+++.>++.<<++++++++++++
+++.>.+++.------.--------.>+.>.

People with nothing to do today can attemp to make an interpreter for the Taxi programming language.

You can even make your own language! There are no limits for this challenge.

Previous challenges

Hi, it's been very long time from last Programming Challenge, and I'd like to revive the tradition.

The point of programming challenge is to create your own solution, and if you're bored, even program it in your favourite programming language. Today's challenge isn't mine. It was created by ČVUT FIKS (year 5, season 2, challenge #4).

You need to transport plans for your quantum computer through Totalitatia. The problem is, that Totalitatia's government would love to have the plans. And they know you're going to transport the computer through the country. You'll receive number N, which denotes number of cities on the map. Then, you'll get M paths, each going from one city to another. Each path has k traffic controls. They're not that much effective, but the less of them you have to pass, the better. Find path from city A to city B, so the maximum number of traffic controls between any two cities is minimal. City A is always the first one (0) and city B is always the last one (N-1).

Input format:

N
M
A1 B1 K1
A2 B2 K2
...

On the first two lines, you'll get numbers N (number of cities) and M (number of paths). Than, on next M lines, you'll get definition of a path. The definition looks like 1 2 6, where 1 is id of first city and 2 is id of second city (delimited by a space). You can go from city 1 to city 2, or from city 2 to city 1. The third number (6) is number of traffic controls.

Output format:

Single number, which denotes maximum number of traffic controls encountered on one path.

Hint: This means, that path that goes via roads with numbers of traffic controls 4 4 4 is better than path via roads with numbers of traffic controls 1 5 1. First example would have output 4, the second one would have output 5.

Example:

IN:

4
5
0 1 3
0 2 2
1 2 1
1 3 4
2 3 5

OUT:

4

Solution: The optimal path is either 0 2 1 3 or 0 1 3.

Bonus

• Describe time complexity of your algorithm.
• If multiple optimal paths exist, find the shortest one.
• Does your algorithm work without changing the core logic, if the source city and the target city is not known beforehand (it changes on each input)?
• Do you use special collection to speed up minimum value search?

Hints

Special collection to speed up algorithm

It's been over a week since the last programming challenge and the previous one was a bit more difficult, so let's do something easier and more accessible to newer programmers in particular. Write a function that takes two strings as input and returns true if they're anagrams of each other, or false if they're not.

Extra credit tasks:

• Don't consider the strings anagrams if they're the same barring punctuation.
• Write an efficient implementation (in terms of time and/or space complexity).
• Minimize your use of built-in functions and methods to bare essentials.
• Write the worst--but still working--implementation that you can conceive of.

Hi everyone, it's been 12 days since last programming challenge. So here's another one. The task is to make an algorithm that'll count how long would it take to fill system of lakes with water.

It's raining in the forest. The forest is full of lakes, which are close to each other. Every lake is below the previous one (so 1st lake is higher than 2nd lake, which is higher than 3rd lake). Lakes are empty at the beginning, and they're filling at rate of 1l/h. Once a lake is full, all water that'd normally fall into the lake will flow to the next lake.

For example, you have lakes A, B, and C. Lake A can hold 1 l of water, lake B can hold 3 l of water and lake C can hold 5 l of water. How long would it take to fill all the lakes?
After one hour, the lakes would be: A (1/1), B (1/3), C(1/5). After two hours, the lakes would be: A(1/1), B(3/3), C(2/5) (because this hour, B received 2l/h - 1l/h from the rain and 1l/h from lake A). After three hours, the lakes would be: A(1/1), B(3/3), C(5/5). So the answer is 3. Please note, that the answer can be any rational number. For example if lake C could hold only 4l instead of 5, the answer would be 2.66666....

Hour 0:

\            /
  ----(A)----
                       \                /
                        \              /
                         \            /
                          ----(B)----
                                             \           /
                                              \         /
                                               \       /
                                               |       |
                                               |       |
                                                --(C)--

Hour 1:

\============/
  ----(A)----
                       \                /
                        \              /
                         \============/
                          ----(B)----
                                             \           /
                                              \         /
                                               \       /
                                               |       |
                                               |=======|
                                                --(C)--

Hour 2:

            ==============
\============/           |
  ----(A)----            |
                       \================/
                        \==============/
                         \============/
                          ----(B)----
                                             \           /
                                              \         /
                                               \       /
                                               |=======|
                                               |=======|
                                                --(C)--

Hour 3:

            ==============
\============/           |
  ----(A)----            |             ========
                       \================/       |
                        \==============/        |
                         \============/         |
                          ----(B)----           |
                                             \===========/
                                              \=========/
                                               \=======/
                                               |=======|
                                               |=======|
                                                --(C)--

Good luck everyone! Tell me if you need clarification or a hint. I already have a solution, but it sometimes doesn't work, so I'm really interested in seeing yours :-)

The programming challenges have kind of come to a grinding halt recently. I think it's time to get another challenge started!

Given a grid of symbols, representing a simple binary state of "filled" or "unfilled", determine whether or not a square is present on the grid. Squares must be 2x2 in size or larger, must be completely solid (i.e. all symbols in the NxN space are "filled"), and must not be directly adjacent to any other filled spaces.

Example, where 0 is "empty" and 1 is "filled":

000000
011100
011100
011100
000010

// Returns true.

000000
011100
011100
011110
000000

// Returns false.

000000
011100
010100
011100
000000

// Returns false.

For those who want a greater challenge, try any of the following:

1. Get a count of all squares.
2. Detect squares that are touching (but not as a rectangle).
3. Detect other specific shapes like triangles or circles (you will need to be creative).
4. If doing (1) and (3), count shapes separately based on type.
5. Detect shapes within unfilled space as well (a checkerboard pattern is a great use case).

It's time for another programming challenge!

Given a list of coordinate pairs on a 2D plane that describe the vertices of a polygon, determine whether the polygon is concave or convex.

Since a polygon could potentially be any shape if we don't specify which vertices connect to which, we'll assume that the coordinates are given in strict order such that adjacent coordinates in the list are connected. Specifically, if we call the list V[1, n] and say that V[i] <-> V[j] means "vertex i and vertex j are connected", then for each arbitrary V[i] we have V[i-1] <-> V[i] <-> V[i+1]. Moreover, since V[1] and V[n] are at the ends of the list, V[1] <-> V[n] holds (i.e. the list "wraps around").

Finally, for simplicity we can assume that all coordinates are unique, that all polygon descriptions generate valid polygons with 3 or more non-overlapping sides, and that, yes, we're working with coordinates that exist in the set of real numbers only. Don't over-complicate it :)

For those who want an even greater challenge, extend this out to work with 3D space!

It's been nearly a week, so it's time for another programming challenge!

This time, let's create a calculator that accepts reverse Polish notation (RPN), also known as postfix notation.

For a bit of background, RPN is where you take your two operands in an expression and place the operator after them. For example, the expression 3 + 5 would be written as 3 5 +. A more complicated expression like (5 - 3) x 8 would be written as 5 3 - 8 x, or 8 5 3 - x.

All your program has to do is accept a valid RPN string and apply the operations in the correct order to produce the expected result.

Another week, another challenge!

This time, assume you're given a grid where each . represents an empty space and each # represents a "wall". We'll call any contiguous space of .s a "region". You can also think of a grid with no walls the "base" region. The walls may subdivide the base region into any number of isolated sub-regions of any shape or size.

Write a program that will, given a grid description, compute the total number of isolated regions.

For example, the following grid has 5 isolated regions:

....#....#
....#.###.
....#.#.#.
#...#..#..
.#..#...#.

It looks like it's been over a week and a half since our last coding challenge, so let's get one going. This challenge is a relatively simple one, but it's complex enough that you can take a variety of different approaches to it.

As the title suggests, write a program that accepts an arbitrary number of arrays, in whatever form or manner you see fit (if you want to e.g. parse a potentially massive CSV file, then go nuts!), and returns a single array containing all of the elements of the other arrays in sorted order. That's it!

Bonus points for creative, efficient, or generalized solutions!

Let's do something a little more challenging this time.

Given an MxN grid of arbitrary size, and given a random starting place on that grid and a list of points to visit, find the shortest path such that you visit all of them. Path lengths will be computed using taxicab distances rather than strict coordinate distance calculations.

There are no restrictions on expected input this time. Output should be the total distance traveled between points.

Example

Assume that we use the character # to denote a spot on the grid, the character @ to denote your starting point, and the character * to denote a place on the grid that you're required to visit. One such grid may look something like this:

######
######
**####
#*####
#*#*##
#@####
######

In this case, let's say that the bottom-left point on the grid is point (0, 0) and we're starting on point (1, 1). One valid solution would be to move to point (3, 2), then (1, 2), then (1, 3), then (1, 4), and finally (0, 4). The shortest path available is thus 8. Note that it's not enough just to visit the next nearest point on the grid!

Another programming mini-challenge for you. It's been a month since the first one and that seemed to be rather successful. (I appreciate that there are other challenges on here but trying to sync with them seems tricky!)

A reminder:
I'm certain that many of you might find these pretty straight forward, but I still think there's merit in sharing different approaches to simple problems, including weird-and-wonderful ones.

KnightBot

Info

You will be writing a small part of a Chess program, specifically focusing on the Knight, on an 8 x 8 board.

Input

The top-left square of the board will have index 0, and the bottom-right square will have index 63.

• The first input is the starting square of the knight.
• The second input is the requested finishing square of the knight.
• The third input is the number of maximum moves allowed.

Output

The expected outcome is either True or False, determined by whether or not the Knight can reach the requested finishing square within the number of allowed moves when stating on the starting square.

e.g. The expected output for the input 16, 21, 4 is True since the Knight can move 16->33->27->21, which is 3 moves.

Extensions

Some additional ideas for extending this challenge...

1. Instead of an 8x8, what if the board was nxn?
2. Instead of "within x moves", what if it was "with exactly x moves?"
3. Instead of a traditional Knight's move (2 long, 1 short), what if it was n long and m short?
4. What if the board was infinite?
5. What if the board looped back around when crossing the edges? (e.g. the square to the right of 7 is 0)

Background

There's been some talk on ~ before, and it seems like there are quite a few people who are either interested in, learning, or working in game development, so I thought this could be a fun programming challenge.

This one is fairly open-ended: make a game in 1 hour. Any game, any engine, don't worry about art or sound or anything.

Doing is the best way to learn. Most people's first project is something overly ambitious, and when they find that it's more difficult than they thought, they can get discouraged, or even give up entirely. This is why the 1 hour limit is important: it forces you to finish something, even if it's small. When you're done, you can come out of it saying you made a game, and you learned from it.

Chances are the game might not be fun, look bad, be buggy, etc. But don't worry about that, everyone's game will have problems, and if you do create something really fun or innovative, congratulations, you have a prototype that you can expand on later!

"Rules"

Like I said before, these "rules" are pretty simple: make a game in (approximately) 1 hour. You can use any tools you want. If you use external assets (art, sound), it's probably best you use something you have the rights to (see resources). If you're completely new to game development/programming, your goal could even be to finish a tutorial.

If you're the kind of person who tends to get carried away with these things, you might want to post a comment saying you're starting, then another one once you've finished your game.

Please share your finished game, I'm sure everyone would love to try them! If your game is web-based, it can be hosted for free on Github Pages or Itch.io. If downloadable, it can be hosted for free on Google Drive, Mega, Dropbox, Itch.io, etc.

Resources

Engines

If you're a beginner, a good engine to start with is LÖVE. It's very simple, and uses Lua, which is very easy to learn.

If you're familiar with another language, you could use a library to make it in that language. Some examples:

C++: SFML, SDL, Allegro

Javascript: kontra, Phaser, pixi.js

Python: pygame

Rust: Piston, ggez, Amethyst

If you want something more complex, consider Godot, Unity, or Unreal.

You can also try something visual like Construct, Clickteam Fusion, or GDevelop

Art

For such a short time constraint, I'd suggest you use your own "programmer art": just use some basic shapes. Your primary focus should be gameplay.

If you think you have time to find something, try looking on OpenGameArt.

Sound

You can make simple sound effects very quickly with sfxr (or in this case, a web port of sfxr called jsfxr).

I've seen the programming challenges on ~comp as well as quite a few users who are interested in getting started with programming. I thought it would be interesting to post some 'mini-challenges' that all could have a go at. I'm certain that many of you might find these pretty straight forward, but I still think there's merit in sharing different approaches to simple problems, including weird-and-wonderful ones.

This is my first post and I'm a maths-guy who dabbles in programming, so I'm not promising anything mind-blowing. If these gain any sort of traction I'll post some more.

Starting of with...

TicTacToeBot

Info

You will be writing code for a programme that will check to see if a player has won a game of tic-tac-toe.

Input

The input will be 9 characters that denote the situation of each square on the grid.

• 'X' represents the X-player has moved on that square.
• 'O' represents the O-player has moved on that square.
• '#' represents that this square is empty.

Example:

|O| |X|
|X|X|O|    The input for this grid will be O#XXXOO##
|O| | |

Output

The expected output is the character representing the winning player, or "#" if the game is not won.

(e.g. The expected output for the example above is '#' since no player has won)

I'm running out of ideas, if you have any, please make your own programming challenge.

This challenge is about designing algorithm to solve this problem.

Let's have game field of size x, y (like in chess). There are two wizards, that are standing at [ 0, 0 ] and are teleporting themselves using spells. The goal is to not be the one who teleports them outside of the map. Each spell teleports wizard by at least +1 tile. Given map size and collection of spells, who wins (they do not make any mistakes)?

Here are few examples:

Example 1

x:4,y:5

Spells: { 0, 2 }

Output: false

Description: Wizard A starts, teleporting both of them to 0, 2. Wizard B teleports them to 0, 4. Wizard A has to teleport them to 0,6, which overflows from the map, so he loses the game. Because starting wizard (wizard A) loses, output is false.

Example 2

x:4,y:4

Spells: { 1,1 }

Output: true

Example 3

x:4,y:5

Spells: { 1,1 },{ 3,2 },{ 1,4 },{ 0,2 },{ 6,5 },{ 3,1 }

Output: true

Example 4

x:400,y:400

Spells: {9,2},{15,1},{1,4},{7,20},{3,100},{6,4},{9,0},{7,0},{8,3},{8,44}

Ouput: true

Good luck! I'll comment here my solution in about a day.

Note: This challenge comes from fiks, programming competition by Czech college ČVUT (CTU).

Hi everyone! There was no coding challenge last week, so I decided to make one this week. If someone wants to make his own challenge, wait few days and post it. I'm running out of ideas and I'd like to keep these challenges running on Tildes.

Everyone here knows data formats - I'm talking about XML or JSON. The task is to make your own format. The format can be as compact as possible, as human-readable as possible, or something that's really unique. Bonus points for writing encoder/decoder for your data format!

How do you handle long texts? Various unicode characters? Complex objects? Cyclic references? It's up to you if you make it fast and simple, or really complex.

I'm looking forward to your data formats. I'm sure they will beat at least csv. Good luck!

Pretty standard:

Write a program that prints the numbers from 1 to 100. But for multiples of three print “Fizz” instead of the number and for the multiples of five print “Buzz”. For numbers which are multiples of both three and five print “FizzBuzz”.

The twist: come up with the most creative or unusual way to solve this in your language of choice.

I just realized that I completely glossed over this week's programming challenge. For this week, let's do something more flexible: write a program that accepts a file as input--either through a file name/path or through standard input--and perform any form of analysis you want on its contents. That's it!

For instance, you could count the occurrences of each word and find the most common ones, or you could determine the average sentence length, or the average unique words per sentence. You could even perform an analysis on changes in words and sentence structure over time (could be useful for e.g. poetry where metre may play an important role). You can stick with simple numbers or dive right into the grittiest forms of textual analysis currently available. You could output raw text or even a graphical representation. You could even do a bit of everything!

How simple or complex your solution ends up being is completely up to you, but I encourage you to challenge yourself by e.g. learning a new language or about different textual analysis techniques, or by focusing on code quality rather than complexity, or even by taking a completely different approach to the problem than you ordinarily would. There are a lot of learning opportunities available here.

Hi everyone! In this challenge, we will build simple genetic algorithm.

The goal is to create genetic algorithm that will learn and output predefined text ("Hello World!").

The goal can be achieved with any language and you'll need just simple loops, collection and knowledge how to create and use objects, even beginners can try to complete this challenge.

How?

I'll try to explain it as best as I can. Genetic algorithms are approximation algorithms - they often do not find the best solution, but they can find very good solutions, fast. It's used when traditional algorithms are either way too slow, or they even don't exist. It's used to, for example, design antennas, or wind turbines. We will use it to write "Hello World".

First of all, we define our Entity. It is solution to given problem, it can be list of integers that describe antenna shape, decision tree, or string ("Hello World"). Each entity contains the solution (string solution) and fitness function. Fitness function says, how good our entity is. Our fitness function will return, how similar is entity solution text to "Hello World" string.

But how will the program work? First of all, we will create list of entities List<Entity>. We will make, for example, 1000 entities (randomly generated). Their Entity.solution will be randomized string of length 11 (because "Hello World" is 11 characters long).

Once we have these entities, we will repeat following steps, until the best entity has fitness == 1.0, or 100% similarity to target string.

First of all, we compute fitness function of all entities. Then, we will create empty list of entities of length 1000. Now, we will 1000-times pick two entities (probably weighted based on their fitness) and combine their strings. We will use the string to create new entity and we will add the new entity to the new list of entities.

Now, we delete old entities and replace them with entities we just made.

The last step is mutation - because what if no entity has the "W" character? We will never get our "Hello World". So we will go through every entity and change 5% (or whatever number you want) of characters in their solution to random characters.

We let it run for a while - and it is done!

So to sum up what we did:

entities <- 1000 random entities
while entities.best.fitness < 1:
  for every entity: compute fitness
  newEntities <- empty list
  1000-times:
    choose two entities from "entities", based on their fitness
    combine solutions of these entities and make newEntity
    newEntities.add(newEntity)
  for every entity: mutate // Randomly change parts of their strings

print(entities.best.solution) // Hello World!

Now go and create the best, fastest, and most pointless, genetic algorithm we've ever seen!

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.

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.