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Project Euler
- ssalmon74 11mo ago[flagged]
- treve 11mo agoNobody is interested in AI commentary.
- vntok 11mo agoThat seems incorrect. This sub-thread is the longest already in this submission, and no other commenter remarked about the parent commenter being an AI.
- rhdunn 11mo agoI've personally found the opposite. In order to advance you need to know the specific techniques or mathematics and there are no hints or information on how to approach the problem. So it boils down to how much of that mathematics you know. If you don't then the brute force approaches take a long time to find the solution.
- leosanchez 11mo agoI think with a few math tricks you can solve around 25-50, It gets very tough after that without maths background.
- rhdunn 11mo agoYeah. I think I got to around 10-15 before I got stuck. It's been several years since I attempted it though.
- btilly 11mo agoI disagree. Often the techniques that you need for a harder problem, are discussed in a forum for an easier problem. Even more often the techniques that you need for a given problem are possible to work out from scratch. And the more you work out, the easier they get. This can be very frustrating for people who are used to being spoon fed techniques, then given problems which use what they have just been taught. But it is a lot of fun for people who enjoy puzzles. If it isn't your cup of tea, that's fine. But don't dismiss it for people who enjoy it. Disclaimer. I haven't personally engaged in the last few years, but I've spent a lot of time on it. I solved 598 and contributed a couple of puzzles as well. One of which they immediately saw a way to do that I hadn't, and put it out there with a difficulty level that I didn't know how to do! That was https://projecteuler.net/problem=240 https://projecteuler.net/problem=240.
- zelphirkalt 11mo agoWait, the math is discussed only in the forums? I thought one is supposed to gain mathematical insight from solving alone. As far as I have read here, forums are only accessible when having an account, which I don't. That would mean to solve later puzzles, I would need an account most likely.
- btilly 11mo agoThe math is not only discussed in the forums. But yes, access to the forums is useful. You get to see not just how you solved the problem, but how others saw and tackled it. And often you'll learn something. That free account really is valuable!
- josh-stylo 11mo agoCompletely agree! Google + Project Euler was how I learned to code
- thornewolf 11mo agoI have done Project Euler very sporadically since high school. To date I've only done problems 1-54. Despite this, I think the website was a big contributor to my love of programming. I found it before knowing about leetcode and I think it prepared me well. I think I owe Project Euler a decent %-age of my eventual entry into Software Engineering as a field.
- ljlolel 11mo agoDitto! Also a great way to learn a new programming language is to try project Euler problems with it.
- Gormisdomai 11mo agoThis website was a part of my education as a computer scientist and seeing it here again I'm curious for the full story of how this site was made. Who made it, what do they do now, is it part of a broader project they have? There is only very basic info here: https://en.wikipedia.org/wiki/Project_Euler https://en.wikipedia.org/wiki/Project_Euler
- observationist 11mo agohttps://archive.is/iEQxy https://archive.is/iEQxy This article is excellent. It mentions the creator, Colin Hughes, and the story behind the project, but it boils down to a passion project for him.
- campbel 11mo agoBack in early 2000s, before hackerrank and similar coding sites, this is what my professors recommended for training programming skills.
- weird-eye-issue 11mo agoYeah my HS CS teacher recommended it but I don't think it was ever required
- Sparkle-san 11mo agoLike many others here, Project Euler was foundational in my education and growth as a programmer. Leonhard Euler himself is an incredible figure and arguably the most prodigious contributor to mathematics throughout history. So much so that people started naming things discovered by him after the next person to have proved them. https://en.wikipedia.org/wiki/List_of_topics_named_after_Leonhard_Euler https://en.wikipedia.org/wiki/List_of_topics_named_after_Leo...
- zelphirkalt 11mo agoMaybe Gauß takes that trophy. To me it felt in mathematics lectures, that Gauß had his hand in everything. Euler might have had that too, but I am not that aware maybe.
- graycat 11mo agoGlanced at the exercises. It appears that two of them have numbers arranged in a triangle and ask for a longest path. Hmm. Given such a triangle, let m be the largest number in the triangle. For each x in the triangle, replace it with m - x. For the resulting triangle, solve it to give the shortest path using one of the well known network shortest path algorithms.
- thaumasiotes 11mo ago> Hmm. Given such a triangle, let m be the largest number in the triangle. For each x in the triangle, replace it with m - x. By the time you've actually done these two steps, you could have already finished the problem with a dynamic programming approach. (Starting from the bottom row and working upward, replace each cell in the row with the length of the longest path from itself to the bottom, which you can know by checking which of its two children has the longer path associated.)
- n4r9 11mo agoThe "well known" path algorithms in this case are overkill; the graph is a tree. And Dijkstra is not really designed to handle negative edge weights (although it would probably function correctly in this instance).
- bre1010 11mo agoI discovered project euler as a novice programmer in high school around 15 years ago. I loved how solving a problem unlocks a secret forum only available to other solvers. I would spend hours reading through everyone's prior solutions and trying to understand them. One guy had tagged his profile as "haskell" but would always provide his solutions in ruby which threw child-me for quite a loop (I actually thought ruby and haskell were the same language for some time)!
- zkmon 11mo agoA great one of my favorite websites of the past. Wonder how they are coping with the issue of their users using AI to solve problems.
- unkulunkulu 11mo agoThe most fun on this site is solving a problem and then having your mind blown by solutions in Apl/j/k and trying to guess what they mean without knowing anything about those languages
- omegaham 11mo agoSee also Uiua, a newcomer to the "extremely cool but completely incomprehensible language" family!
- taeric 11mo agoEven better than the crazy languages, is seeing some fundamental math used to prevent having to do a ridiculously expensive search. That said, raw brute force often did far better than you'd like to admit.
- debatem1 11mo agoThe biggest thing I learned from PE was that neither elegant theory nor brute force had a monopoly on successful optimization strategies. It's been something I've carried with me ever since and has over and over again proven its value. A real gem of a resource.
- gcanyon 11mo agoI've solved about a hundred PE problems in Livecode, maybe 40 in Python, and about 20 in J. I highly recommend giving it a try in a language you don't know, it's fun! Especially with something as obscure as J.
- carlyai 11mo agoright
- matthewaveryusa 11mo agoI attribute project euler for instilling the playful enjoyment of writing programs in college while I was studying electrical and computer engineering. I owe my career to it!
- 0x1ch 11mo agoI remember visiting Project Euler back in 2013/14 or so. Was really my first introduction to programming exercises as youngin. Probably did fifteen or so of them before ADHD kicked in though. A small gem on the web.
- codexb 11mo agoWow, I can't believe this is still around! I'm glad to see artifacts from the past like this are still out there on the internet. Makes me miss Google CodeJam though.
- ketanmaheshwari 11mo agoI solved a few using AWK, fun: https://github.com/ketancmaheshwari/projecteuler https://github.com/ketancmaheshwari/projecteuler
- mjcohen 11mo agoDid you use the regular version or the one with multiple-precision values?
- ketanmaheshwari 11mo agoI used the regular version. Actually, I don't even know what is multiple-precision values -- will look it up.
- n4r9 11mo agoAfter learning AWK I realised it could be used really neatly for problem 67. I remember it was blazing fast, orders of magnitude faster than Python
- nik9000 11mo agoI ranked on that once! I was like the 23rd person to do one of the new problems one time. Just about as low as you can rank. It was a fun puzzle but you had to be awake at a funky time to do it.
- sizzzzlerz 11mo agoi was a euler fanatic some years ago reaching problems in the 500s albeit, skipping problems along the way. at that point, too many problems required a deeper math background than i possessed so i abandoned it. what amazed me was that others composed solutions that solved problems in mere milliseconds that brute force approaches would still be running when the universe cooled to absolute zero.
- rbongers 11mo agoI only reached the 100s back in the day. What amazed me was that it seemed like every problem had a paper solution, when it would take any computer algorithm thousands or millions of computations to solve the same problem.
- rufus_foreman 11mo agoI played around with some of the easier problems, my favorite was a couple times when starting with the obvious brute force solution in code and then refactoring and simplifying it iteratively ended up getting me the paper solution.
- theoldgreybeard 11mo agoI love running euler problems when trying to learn the basics of a new programming language. I have a small collection of programs in like 10 different languages that I keep around as a reference for things because I always try to use language-specific features to solve the problems, and then I reference them as examples.
- gregdeon 11mo agoWow. You reminded me of a computer engineering class years ago where we wrote assemblers and emulators for a simple architecture. I tested mine by writing a solution for one of the first Project Euler questions!
- theoldgreybeard 11mo agoI still have my Oberon-2 compiler from my compilers class and a handful of Euler questions I used to test it.
- callc 11mo agoI too owe had my love for programming captured through project Euler. I am immensely grateful to my maths prof who introduced me to it. I also love looking back at my old PE code and having absolutely no idea what it doing. No comments, no docs, no notes. From a different era.
- sbmthakur 11mo agoHackerrank also used to host(still has?) PE problems with additional test cases.
- nurettin 11mo ago2007 I remember writing one-liner ruby solutions up to 100.
- Imnimo 11mo agoThese are both a lot more fun, and a lot more educational than leetcode problems. Strongly recommend for anyone looking for practice problems when learning a new language or whatever.
- BeetleB 11mo agoHa! I did a lot of these around 2007-2008. I solved the first 100 or so ones. Solving these were more fun than any other programming problems site I've seen. I quit it when I realized I was spending 4+ hours per problem - I couldn't justify the time. Beyond a certain point, most required some knowledge of elementary number theory.
- coef2 11mo agoI agree with you. About a decade ago, I got really tired of coding interview prep. I somehow ended up getting into Project Euler and worked through the first 100 problems. It was a great way to learn a bit of number theory and regain my interest in programming.
- goalieca 11mo agoSame timeline for me! This was my great procrastination side quest during grad school. I learned haskell and a bit of ocaml working on these. Functional languages are extremely well suited to these kinds of problems.
- misja111 11mo agoSame for me, the first 100 are doable, after that they take more and more time and require deeper mathematical knowledge. Which is nice as well, but at some point I started to wonder if it wouldn't be better if I spent all that time on learning some more practical knowledge.
- pkoird 11mo agoI remember it vaguely but there used to be a badge awarded for being among the first 100 people to solve the problem. I was obsessed with getting that badge to the point that I spent obscene amount of time solving the-then recently released problem even when the following day was my final exams. I did manage to get that badge though. This was circa 2013. Fun times!
- anthk 11mo agoThanks for reminding me this; I'd try to solve them both in Scheme (s9fes) and JimTCL.
- shaunxcode 11mo agothis is how you end up getting into APL/array langs for sure.
- rajandatta 11mo agoSecond this ... have been writing some solutions in Kap, an APL like variant. It's stunning to see 20+ idiomatic solutions in one screen as many problems can be solved in a compact manner. The elegance really reminds one of why we fell in love with Programming in the first place
- meken 11mo agoOne of my best memories was in undergrad there was one semester in 2013 where half a dozen of my CS classmates and I competed to try and solve the most Project Euler problems. We had a leaderboard and everything. I saw first hand how much faster my friend’s Java solutions were than my Python solutions. Good times.
- aiahs 11mo agoI did a lot of these when I was around 15-16 and it solidified for me my interest in CS but in general abstract thinking and problem solving. Great site.
- darylteo 11mo agoHow I learnt about prime number sieves. Good prep for Advent of Code in 2 weeks.
- davidhariri 11mo agoI learned so much from this site- including that so much education comes from being prompted to ask the right questions.
- deleted 11mo ago[deleted]
- peterkagey 11mo agoI wrote Problem 619 (https://projecteuler.net/problem=619 https://projecteuler.net/problem=619) which was published on 2018-01-27 and solved by 474. The problem was based on 2013 Putnam Exam problem A2 (https://kskedlaya.org/putnam-archive/2013.pdf https://kskedlaya.org/putnam-archive/2013.pdf) which I took at the end of undergrad. I got an email six years later (in November 2024) telling me they accepted the problem: Greetings! Please excuse the email. It's quite possible that you are no longer active at Project Euler, but we are currently trying to retrospectively acknowledge contributors of problems. You were identified as being involved with Square subsets [619 m] in Sep-17. If you would like to be added as a verified contributor, please reply to this email and provide the username you currently use at projecteuler.net. Please note that contributor usernames will not appear publicly, rather they will be used internally to unlock new contributor awards we are introducing. Regards, Project Euler Team
- webo 11mo agoI was curious if LLMs are good for this problem. ChatGPT-5.1-Thinking one-shotted a correct Python script without any library use (https://pastecode.io/s/jg6ggxpm https://pastecode.io/s/jg6ggxpm). Claude Opus failed to solve after trying for a while.
- whimsicalism 11mo agoproject euler problems are likely in the RL corpora
- mvdtnz 11mo agoFirst of all, don't do this. No one cares. Secondly obviously every Euler solution is going to appear in the training data many times over. It's no surprise at all that an LLM can regurgitate data that was given to it.
- kragen 11mo agoI thought it was interesting, and I wouldn't be surprised if Euler solutions weren't in the training data, especially for the later problems like this one.
- kekqqq 11mo agoNo one tells you that they delete inactive accounts. I used to have over 300 solved problems htere. Now it is all gone, all the effort, but the skill remained of course.
- inasio 11mo agoA few years back (10 maybe?) they had a disk crash, and there was a notice that for people with 100 or more problems solved they'd do an extra effort to recover their solutions and add you back, not sure if it was only posted on the main website. I was lucky to get my account back at the time
- kekqqq 11mo agoAh okay, I was active there 9-12 years ago, so it migh been before the crash. I remember checking it, however, 7 years ago, and I was still able to log in.
- yogsototh 11mo agoI remember there were data loss, but my account appears to have been recovered. You may try to login again, and with luck, like me you will get back your history.
- doodpants 11mo agoSo, I gather that you treated your solutions as throw-away code, rather than keeping them? Kind of surprising, considering that some problems build off of each other, or otherwise benefit from sharing code; you never know when the code for one solution could be useful later. For example, a prime number generator/tester is necessary for many of the problems. (I have all my solution code, in source control no less, so if I ever lost my account, I could just run them all and re-enter the solutions.)
- kekqqq 11mo ago> So, I gather that you treated your solutions as throw-away code, rather than keeping them? I kept the code that I found clever or useful, but I had a very borderline approach to archiving my stuff in general back then. I was still in high school.
- deleted 11mo ago[deleted]
- medbar 11mo agovery surprised this project is still releasing problems weekly - I remember this being up when I was in high school. maybe I'll pick it up again since I only did the first ~30 or so back then.
- philiplu 11mo agoNot only are they still releasing problems weekly, they have a long backlog of problems waiting for release. I submitted a problem back in April 2024, and it didn't get published until October 2025 (problem 963). There's an excellent core development team that works with problem-submitters to get problems tuned up for Project Euler.
- senderista 11mo agoSo much more fun than leetcode. OTOH, unlikely to help you in an interview.
- cmpalmer52 11mo agoIt would help you if I were doing the interview…
- akudha 11mo agoAre there other similar sites? I remember this one, for bioinformatics https://rosalind.info/problems/list-view/ https://rosalind.info/problems/list-view/
- mrgoldenbrown 11mo agoI like Advent of Code. Pretty popular, and more general purpose programming puzzles rather than euler, which tends to be pure math focused. https://adventofcode.com/ https://adventofcode.com/
- phil-pickering 11mo agoI think a hat-tip is due to freeCodeCamp for introducing Project Euler (along with Rosetta Code) to a new generation of programmers: https://www.freecodecamp.org/learn/project-euler/#project-euler-problems-1-to-100 https://www.freecodecamp.org/learn/project-euler/#project-eu...
- fiftyacorn 11mo agoi think its a decent environment to do the programs - ok restrictive to js but lets you focus on the problems
- SethTro 11mo agoI wrote Problem 371, https://projecteuler.net/problem=371 https://projecteuler.net/problem=371 , as a high school student in 2012! I'm so happy to have spent twenty years of my life learning math and solving problems on Project Euler and elsewhere.
- dekhn 11mo agoInteresting- I ask a license plate question (when will california run out of plates in its current serialization format, based on a couple of plates observed in two different years). It's a much simpler question, though (just linear extrapolation).
- am17an 11mo agoThis is one of my favourite problems, I still remember that it has a very real edge case even though I solved it more than 10 years ago. Thank you for the problem!
- knollimar 11mo agoCan you reuse a plate with 500?
- hatthew 11mo agoThe wording seems to strongly imply no; you need two separate plates with 500 on them.
- SethTro 11mo agoI'm glad you enjoyed! It was a real game I played when driving around.
- JohnLocke4 11mo agoIs your real name also Seth? This is wholesome and hilarious
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- fortranfiend 11mo agofake frustration yet another thing named after euler.
- pveierland 11mo agoWhat's really neat is that most of the problems are so compact that you can just read about the full problem, then spend hours and days thinking about possible solutions. I created a PDF version that I keep on my Remarkable for puzzling: https://github.com/pveierland/project_euler_offline https://github.com/pveierland/project_euler_offline
- emerongi 11mo agoThank you for the PDF version!
- theotherpablo 11mo agoAnyone else having problems registering or is my solution wrong?
- theotherpablo 11mo agoAnyone else having problems registering? or is my solution to Problem Zero wrong...
- sega_sai 11mo agoThere is a somewhat similar idea behind "Ponder This" by IBM https://research.ibm.com/haifa/ponderthis/index.shtml https://research.ibm.com/haifa/ponderthis/index.shtml They post a problem every month and in the end post a solution. I used to spend a bit too much time on those.
- hintymad 11mo agoThe difference is that Ponder This is harder than the average problems in Euler Project, and requires higher level of mathematical maturity.
- DiabloD3 11mo agoSo, to remind myself, Euler's name is pronounced more like Oiler, right?
- nimih 11mo agoThat's how I was taught, and Wikipedia agrees (and even provides audio clips alongside the IPA and English phonetic transcriptions).
- schlauerfox 11mo agoI love a good puzzle solving club. Some of my favorites: https://www.themastertheorem.com/ https://www.themastertheorem.com/ https://en.wikipedia.org/wiki/Perplex_City https://en.wikipedia.org/wiki/Perplex_City https://en.wikipedia.org/wiki/MindTrap https://en.wikipedia.org/wiki/MindTrap
- butifnot0701 11mo agoThe leetcode before leetcode. Hail.
- RandyOrion 11mo agoAfter opened https://projecteuler.net/ https://projecteuler.net/ I got 403 Forbidden Request forbidden by administrative rules. Note: I didn't know and open this website until now.
- kragen 11mo agoWell, that sucks!
- dhbradshaw 11mo agoProject Euler was what I used to get comfortable with my two main languages -- first python and then rust. I loved to solve it and then look through all the different solutions and find pretty ideas and idioms.
- varyherb 11mo agoProject Euler spurred my love for math and programming when I was 15. I got through the first few with pencil and paper and then quickly realized I was going to need to learn how to program. Got started with Java (in Eclipse) and then moved on to Python. I feel like it completely changed the trajectory of my life.
- seeknotfind 11mo agoThousand of hours on this. Love it.
- leosanchez 11mo agoSince this is still on HN frontpage. Does anyone suggest any math books to help solve these problems. I am pretty sure you can't solve problems above 50 without strong maths background.
- siddboots 11mo agoConcrete Mathematics is probably the best single book that you could read to prepare you for some the problems beyond the first 50. It’s extremely fun, and also mathematically serious. A large portion of PE problems are exactly in the cross sections of number theory, combinatorics, and computation that is covered in this book. https://en.wikipedia.org/wiki/Concrete_Mathematics https://en.wikipedia.org/wiki/Concrete_Mathematics
- mapehe 11mo agoThis is such a great site.
- cambaceres 11mo ago12 years ago I was a failed computer science student, wasting my time on drugs. Having failed so many classes I did not see any future at all, and I was considering killing myself to get out of the anxiety and stress. My confidence regarding programming etc was 0. I decided to apply for a junior developer job. I got an interview and to prepare for an interview I found this site, Project Euler. I did ten or so tasks. The interview started out pretty bad, they asked me some technical questions which I did not give good answers to, and I saw that they where not impressed. Then they wanted me to solve two programming problems on a white board. Imagine the relief I felt when both of these questions where from the ones that I solved on Project Euler a couple of days before! I nailed them and the interviewers where clearly impressed. In the end they hired me and motivated it with that although I lack a lot of theory I am obviously a very good coder haha. Anyway, that was what I needed, when I got this job I quit the drugs and got my act together. 12 years later I live a confortable life as a freelancer and have even managed to build my own SaaS with paying customers! Thank you Project Euler.
- sarreph 11mo agoGood for you! Inspiring stories like yours are positive externalities that will no longer be extant in the same way when everyone’s minds are just thin clients on top of LLMs!
- mchaver 11mo agoGreat story. Are you willing to share more about your SaaS?
- cambaceres 11mo agoI'd love to but I can't be too specific due to the personal stuff I shared in the original comment. It's a system that helps services companies within a certain industry to digitalize all their paperwork, report to the national goverment agencies etc. They do a lot of manual work which can be digitalized easily. I found this opportunity by just randomly throwing out in a big community that I build software and is looking for ideas, and some guy answered that ended up being my business partner for 3 years now. We are not rich from it but earn like $2000 each a month after tax which is quite a lot for us since we live in a country where healthcare, schools, parental leave etc are covered by taxes. And we dont need to put more than a few hours a month on support. I have put in basically all my spare time for 2 years to get to this point though, the biggest reward is not the money but the process of sitting through the nights being completely in the zone and building this stuff knowing that it will be great :D
- lll-o-lll 11mo agoWhelp, the opening “problem zero” stuffed me up. > A number is a perfect square, or a square number, if it is the square of a positive integer. For example, is a square number because ; it is also an odd square. The first 5 square numbers are: , and the sum of the odd squares is . Among the first 881 thousand square numbers, what is the sum of all the odd squares? I wanted to use Uiua, and hence: /+ⁿ2+1⍜÷⇡ 2 881000 But Uiua doesn’t support big ints, just f64. So yuck, python to get an accurate answer. Just sad now.
- wodenokoto 11mo agoHow did you get to problem 0? When I look at the list of problems it starts at 1: https://projecteuler.net/archives https://projecteuler.net/archives
- lll-o-lll 11mo agoIt’s the “sign up” challenge
- janislaw 11mo agoThis will become a practice of implementing bignums in your language of choice, which is a valuable exercise itself.
- gcanyon 11mo agoI did this (bignum) library for Livecode specifically for PE. https://github.com/gcanyon/bignum https://github.com/gcanyon/bignum
- robert-zaremba 11mo agoDuring my university time, I used to do a lot of different programming puzzles and algo. I think it an invaluable training that every serious engineer should try without relaying on AI. Skills are trained by practice and thinking. Skilled people will never be subsidized by AI. Unskilled juniors, who don't train properly will go into tranches (as it's already happening).
- mpcsb 11mo agoI thank project Euler because whenever I face some coding challenge that has any mathematical inclination, I will(!) impress interviewers. I spent a lot of time on it, and learned a considerable amount of theory and hacks. What a privilege to be able to do this, instead of digging the fields and other manual labor. Thanks culture!
- ethin 11mo agoI was trying to create an account but it kept saying the confirmation code was wrong. Idk if that's a bug but... I was using the audio captcha. Still, the website seems pretty neat!
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