Physicists have created a theoretical "Quantum Rubik's Cube" where the colored squares exist in superimposed states. Unlike a classical Rubik's Cube, rotations can entangle the squares, making the puzzle significantly more complex. Researchers developed an algorithm to solve this quantum puzzle, focusing on maximizing the probability of reaching the solved state, rather than guaranteeing a solution in a specific number of moves. They discovered that counterintuitive moves, ones that seemingly scramble the cube, can actually increase the likelihood of ultimately solving it due to the nature of quantum superposition and entanglement.
A blog post challenges readers to solve a math puzzle involving predicting the output of a hypothetical AI model trained on specific numerical sequences. The AI, named "Predictor," is trained on sequences like 1,2,3,4,5 -> 6 and 2,4,6,8,10 -> 12, seemingly learning to extrapolate the next number in simple arithmetic progressions. However, when given the sequence 1,3,5,7,9, the AI outputs 10 instead of the expected 11. The puzzle asks readers to determine the underlying logic of the AI and predict its output for the sequence 1,2,3,5,8. A symbolic prize (bragging rights) is offered to anyone who can crack the code.
HN users generally found the AI/Math puzzle unimpressive and easily solvable. Several commenters quickly pointed out the solution involves recognizing the pattern as powers of 2, leading to the answer 2^32. Some criticized the framing as an "AI" puzzle, arguing it's a straightforward math problem solvable with basic pattern recognition. Others debated the value of the $100 prize and whether it justified the effort. A few users noted potential ambiguity in the problem's wording, but these concerns were largely dismissed by others who found the intended pattern clear. There was some discussion about the puzzle's suitability for testing AI, with skepticism expressed about its ability to distinguish genuine intelligence.
William Bader's webpage showcases his extensive collection of twisty puzzles, particularly Rubik's Cubes and variations thereof. The site details numerous puzzles from his collection, often with accompanying images and descriptions of their mechanisms and solutions. He explores the history and mechanics of these puzzles, delving into group theory, algorithms like Thistlethwaite's and Kociemba's, and even the physics of cube rotations. The collection also includes other puzzles like the Pyraminx and Megaminx, as well as "magic" 8-balls. Bader's site acts as both a personal catalog and a rich resource for puzzle enthusiasts.
HN users generally enjoyed the interactive explanations of Rubik's Cube solutions, praising the clear visualizations and step-by-step approach. Some found the beginner method easier to grasp than Fridrich (CFOP), appreciating its focus on intuitive understanding over speed. A few commenters shared their personal experiences learning and teaching cube solving, with one suggesting the site could be improved by allowing users to manipulate the cube directly. Others discussed the mathematics behind the puzzle, touching on group theory and God's number. There was also a brief tangent about other twisty puzzles and the general appeal of such challenges.
Feudle is a daily word puzzle game inspired by Family Feud. Players guess the most popular answers to a given prompt, with an AI model providing the top responses based on survey data. The goal is to find all the hidden answers within six guesses, earning more points for uncovering the most popular responses. Each day brings a fresh prompt and a new challenge.
HN commenters discuss Feudle, a daily word puzzle game using AI. Some express skepticism about the claimed AI integration, questioning its actual impact on gameplay and suggesting it's primarily a marketing buzzword. Others find the game enjoyable, praising its simple but engaging mechanics. A few commenters offer constructive criticism, suggesting improvements like allowing multiple guesses and providing clearer feedback on incorrect answers. Several note the similarity to other word games, particularly Wordle, with some debating the merits of Feudle's unique "feud" theme. The lack of open-source code is also mentioned, raising questions about the transparency of the AI implementation.
Daniel Chase Hooper created a Sudoku variant called "Cracked Sudoku" where all 81 cells have unique shapes, eliminating the need for row and column lines. The puzzle maintains the standard Sudoku rules, requiring digits 1-9 to appear only once in each traditional row, column, and 3x3 block. Hooper generated these puzzles algorithmically, starting with a solved grid and then fracturing it into unique, interlocking pieces like a jigsaw puzzle. This introduces an added layer of visual complexity, making the puzzle more challenging by obfuscating the traditional grid structure and relying solely on the shapes for positional clues.
HN commenters generally found the uniquely shaped Sudoku variant interesting and visually appealing. Several praised its elegance and the cleverness of its design. Some discussed the difficulty of the puzzle, wondering if the unique shapes made it easier or harder to solve, and speculating about solving techniques. A few commenters expressed skepticism about its solvability or uniqueness, while others linked to similar previous attempts at uniquely shaped Sudoku grids. One commenter pointed out the potential for this design to be adapted for colorblind individuals by using patterns instead of colors. There was also brief discussion about the possibility of generating such puzzles algorithmically.
Hillel Wayne presents a seemingly straightforward JavaScript code snippet involving a variable assignment within a conditional statement containing a regular expression match. The unexpected behavior arises from how JavaScript's RegExp object handles global flags. Because the global flag is enabled, subsequent calls to test() within the same regex object continue matching from the previous match's position. This leads to the conditional evaluating differently on subsequent runs, resulting in the variable assignment only happening once even though the conditional appears to be true multiple times. Effectively, the regex remembers its position between calls, causing confusion for those expecting each call to test() to start from the beginning of the string. The post highlights the subtle yet crucial difference between using a regex literal each time versus using a regex object, which retains state.
Hacker News users discuss various aspects of the perplexing JavaScript parsing puzzle. Several commenters analyze the specific grammar rules and automatic semicolon insertion (ASI) behavior that lead to the unexpected result, highlighting the complexities of JavaScript's parsing logic. Some point out that the ++ operator binds more tightly than the optional chaining operator (?.), explaining why the increment applies to the property access result rather than the object itself. Others mention the importance of tools like ESLint and linters for catching such potential issues and suggest that relying on ASI can be problematic. A few users share personal anecdotes of encountering similar unexpected JavaScript behavior, emphasizing the need for careful consideration of these parsing quirks. One commenter suggests the puzzle demonstrates why "simple" languages can be more difficult to master than initially perceived.
Dr. Drang poses a puzzle from the March 2025 issue of Scientific American, involving a square steel plate with a circular hole and a matching square-headed bolt. The challenge is to determine how much the center of the hole moves relative to the plate's center when the bolt is tightened, pulling the head flush against the plate. He outlines his approach using vector analysis, trigonometric identities, and small-angle approximations to derive a simplified solution. He compares this to a purely geometric approach, also presented in the magazine, and finds it both more elegant and more readily generalizable to different hole/head sizes.
HN users generally found the puzzle trivial, with several pointing out the quick solution of simply measuring the gap between the bolts to determine which one is missing. Some debated the practicality of such a solution, suggesting calipers would be necessary for accuracy, while others argued a visual inspection would suffice. A few commenters explored alternative, more complex approaches involving calculating the center of mass or using image analysis software, but these were generally dismissed as overkill. The discussion also briefly touched on manufacturing tolerances and the real-world implications of such a scenario.
The Hacker News post presents a betting game puzzle where you predict the sum of your neighbors' bets, with the closest guess winning. The challenge is to calculate this sum efficiently when dealing with a large number of players, each choosing a bet from 0 to 9. The author shares a clever algorithm that achieves this in linear time, utilizing a frequency array to avoid redundant calculations. This approach significantly improves performance compared to a naive quadratic solution, making the game scalable for a substantial number of participants.
Hacker News users discussed the efficiency and practicality of the presented algorithm for the betting game puzzle. Some questioned the "linear time" claim, pointing out the algorithm's reliance on a precomputed lookup table, the creation of which would not be linear. Others debated the best way to construct such a table efficiently. A few commenters suggested alternative approaches, including using Gray codes or focusing on bit manipulation tricks. There was also discussion about the problem's framing, with some arguing it's more of a dynamic programming exercise than a puzzle. Finally, some users explored variations of the puzzle, such as changing the allowed bet sizes or considering non-integer bets.
Bracket City is a daily online word puzzle that deconstructs the traditional crossword format. Instead of a grid, clues are presented in a bracket-style tournament, where players choose the correct answer from two options to advance. Each correct answer reveals letters that eventually combine to form the final solution word. This unique presentation adds a layer of strategy and deductive reasoning, as incorrect choices don't just leave a gap, but actively lead down the wrong path. The daily puzzle offers a fresh take on wordplay, challenging players to not just know the answers, but also to understand the relationships between them.
Hacker News users discussed the unusual format and difficulty of Bracket City. Several commenters found the puzzle too challenging, describing it as "obtuse" and expressing frustration with the lack of clear instructions or feedback. The unconventional grid and scoring system also drew criticism. Some users questioned the puzzle's description as a crossword, suggesting alternative classifications like a logic puzzle or code-breaking challenge. Despite the difficulty, some commenters expressed intrigue and a desire to understand the solving process better, with one suggesting a walkthrough or tutorial would be helpful. Others appreciated the novelty and different approach to puzzling, even if they found it personally too hard. The puzzle's creator responded to some comments, clarifying certain mechanics and acknowledging the steep learning curve.
Figgie, created by Jane Street, is a trick-taking card game played with a 60-card deck featuring six suits. Players bid on how many tricks they think they can win, with a unique twist: suits are ranked differently each round, adding a layer of strategic complexity. The goal is to accurately predict and achieve your bid, earning points based on successful predictions. The game encourages strategic thinking by requiring players to consider both card strength and the fluctuating suit hierarchy when making bids and playing tricks.
HN commenters discuss Figgie, a card game developed by Jane Street, with some expressing interest in trying it out due to Jane Street's reputation. Several commenters compare it to existing trick-taking games, mentioning similarities to Spades, Bridge, and Hearts. Some express skepticism about the complexity, wondering if it's genuinely intricate or just unnecessarily convoluted. The lack of a physical deck is a point of contention, with some preferring a tangible game experience. Others are intrigued by the strategy and mathematical elements, highlighting the dynamic partnership aspect and the potential for deep analysis. A few commenters note the similarity between "Figgie" and the word "fig," speculating about the name's origin.
SQL Noir is a free, interactive tutorial that teaches SQL syntax and database concepts through a series of crime-solving puzzles. Players progress through a noir-themed storyline by writing SQL queries to interrogate witnesses, analyze clues, and ultimately identify the culprit. The game provides immediate feedback on query correctness and offers hints when needed, making it accessible to beginners while still challenging experienced users with increasingly complex scenarios. It focuses on practical application of SQL skills in a fun and engaging environment.
HN commenters generally expressed enthusiasm for SQL Noir, praising its engaging and gamified approach to learning SQL. Several noted its potential appeal to beginners and those who struggle with traditional learning methods. Some suggested improvements, such as adding more complex queries and scenarios, incorporating different SQL dialects (like PostgreSQL), and offering hints or progressive difficulty levels. A few commenters shared their positive experiences using the platform, highlighting its effectiveness in reinforcing SQL concepts. One commenter mentioned a similar project they had worked on, focusing on learning regular expressions through a detective game. The overall sentiment was positive, with many viewing SQL Noir as a valuable and innovative tool for learning SQL.
SudokuVariants.com lets you play and create a wide variety of Sudoku puzzles beyond the classic 9x9 grid. The website offers different grid sizes, shapes, and rule sets, including variations like Killer Sudoku, Irregular Sudoku, and even custom rule combinations. Users can experiment with existing variants or design their own unique Sudoku challenges using a visual editor, and then share their creations with others via a generated link. The site aims to provide a comprehensive platform for both playing and exploring the vast possibilities within the Sudoku puzzle format.
Hacker News users generally expressed interest in the SudokuVariants website. Several praised its clean design and the variety of puzzles offered. Some found the "construct your own variant" feature particularly appealing, and one user suggested adding a difficulty rating system for user-created puzzles. A few commenters mentioned specific variant recommendations, including "Killer Sudoku" and a variant with prime number constraints. There was also a brief discussion about the underlying logic and algorithms involved in generating and solving these puzzles. One user pointed out that some extreme variants might be NP-complete, implying significant computational challenges for larger grids or complex rules.
Summary of Comments ( 2 )
https://news.ycombinator.com/item?id=43746868
HN commenters were generally skeptical of the article's framing. Several pointed out that the "quantum Rubik's cube" isn't a physical object, but a theoretical model using quantum states analogous to a Rubik's cube. They questioned the practicality and relevance of the research, with some suggesting it was a "solution in search of a problem." Others debated the meaning of "optimal solution" in a quantum context, where superposition allows for multiple states to exist simultaneously. Some commenters did express interest in the underlying mathematics and its potential applications, although these comments were less prevalent than the skeptical ones. A few pointed out that the research is primarily theoretical and explorations into potential applications are likely years away.
The Hacker News post titled "Physicists Designed a Quantum Rubik's Cube and Found the Best Way to Solve It" generated several comments, many of which delve into the nuances of the research and its implications.
Several commenters discussed the nature of the "quantum Rubik's cube" itself. Some pointed out that it wasn't a physical object but rather a theoretical model represented by a quantum system. This led to discussions about the differences between manipulating a physical Rubik's cube and manipulating a quantum state. One commenter specifically highlighted the distinction between physical rotations and unitary transformations applied to the quantum system.
The concept of "solving" the quantum Rubik's cube also sparked debate. Commenters clarified that the research wasn't about finding a sequence of moves like in a classical Rubik's cube, but rather about finding the optimal quantum gate sequence to transform a given quantum state into a target state. This involved discussions about quantum gates, unitary transformations, and the complexity of these operations.
The topic of optimization was also prominent. Commenters explained that the researchers used a specific optimization algorithm (GRAPE) to find the most efficient way to perform the state transformation. This led to discussions about the computational cost of these calculations and the potential applications of such optimization techniques in other quantum computing problems.
Some comments focused on the practical implications of this research. While acknowledging the theoretical nature of the work, some commenters speculated about potential applications in quantum information processing and quantum control. Others questioned the immediate practical relevance, emphasizing that this was fundamental research.
One commenter expressed skepticism about the novelty of the research, suggesting that the problem being addressed was already well-known in quantum control theory. This prompted counter-arguments from other commenters who defended the value of the research, emphasizing the specific contributions made by the authors.
Finally, some comments addressed the accessibility of the original article and the ScienceAlert summary. Some appreciated the simplified explanation provided by ScienceAlert, while others expressed a desire to delve into the more technical details presented in the original research paper.