Search found 25 matches

by yourmaths
Wed Jun 05, 2019 12:23 am
Forum: Clarifications on Project Euler Problems
Topic: Problem 610
Replies: 16
Views: 2026

Re: Problem 610

Hello. I solved 610 last night, and DJohn's post was helpful in formulating my solution. To be clear, in answering the problem, CMD is indeed considered invalid, as well as many of the other examples in the thread for problem 89 . However, I'm not sure that this is definitively ruled out by the Abou...
by yourmaths
Fri Apr 26, 2019 1:48 am
Forum: Clarifications on Project Euler Problems
Topic: Problem 285
Replies: 17
Views: 7175

Re: Problem 285

jpaulson wrote:
Fri Nov 28, 2014 4:37 am
I believe the values posted for k=1000 and k=10000 earlier in this thread were wrong. My AC program gets:
k=1,000 => 1556.18298
k=10,000 => 15688.74566
I have just completed this problem and I can confirm that these are the correct values. I'm not sure what is going on in the rest of this thread.
by yourmaths
Tue Mar 05, 2019 10:57 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 641
Replies: 5
Views: 1796

Re: Problem 641

A Long Row of Dice. No kidding. By my calculations, that many dice in a row is many orders of magnitude longer than the length of the observable universe.
by yourmaths
Wed Nov 14, 2018 9:45 am
Forum: Clarifications on Project Euler Problems
Topic: Problem 521
Replies: 9
Views: 3430

Re: Problem 521

There are plenty of test solutions in these forums... maybe the rule needs to be clarified?
by yourmaths
Fri Nov 02, 2018 11:05 am
Forum: Number Theory
Topic: Project Euler Factoring Challenge
Replies: 4
Views: 4576

Re: Project Euler Factoring Challenge

I thought more people would get into this, but anyway I factored the 80 digit number with the quadratic sieve.
I started coding the number field sieve algorithm but have gotten stuck on the square root problem.
by yourmaths
Thu Oct 18, 2018 12:24 am
Forum: Clarifications on Project Euler Problems
Topic: Problem 272
Replies: 14
Views: 6029

Re: Problem 272

For future solvers: if you end up getting the correct wrong answer above, you are about 95% there, and understand the problem well enough to identify the issue and solve it.
by yourmaths
Wed Oct 17, 2018 7:44 am
Forum: Clarifications on Project Euler Problems
Topic: Problem 272
Replies: 14
Views: 6029

Re: Problem 272

Could anyone confirm that: 1) there are 663 positive results for n <= 3 * 10^7 for a total of 13166591472. 2) there are 29454 positive results for n <= 3 * 10^8. Thanks. Strangely enough, I get these wrong results as well EDIT: found my issue. Though I probably can't say too much about it. OK I hav...
by yourmaths
Tue Sep 11, 2018 10:31 am
Forum: Recreational
Topic: Suggest me a book
Replies: 13
Views: 5984

Re: Suggest me a book

My "go to" book is "Elementary Number Theory" by David M. Burton. I don't even know where I got it from but the main thing I like about it is that the mathematical detail is interspersed with interesting historical details. Both "Prime Numbers: A Computational Perspective", Pomerance & Crandall, and...
by yourmaths
Tue Sep 11, 2018 10:21 am
Forum: News, Suggestions, and FAQ
Topic: ProjectEuler.net "Level"
Replies: 3
Views: 1696

Re: ProjectEuler.net "Level"

:D
by yourmaths
Mon Sep 10, 2018 11:34 pm
Forum: News, Suggestions, and FAQ
Topic: ProjectEuler.net "Level"
Replies: 3
Views: 1696

Re: ProjectEuler.net "Level"

Just Curious -- How is it that some posts include the author's Project Euler (Problems solved) "Level" and most do not? I tried looking at my UserControlPanel/Profile/EditSignature and elsewhere but this is yet another Project Euler riddle I can't solve! Just type the following into your signature ...
by yourmaths
Tue Sep 04, 2018 9:17 am
Forum: Number Theory
Topic: An Infinite Prime Number Generator
Replies: 5
Views: 3039

Re: An Infinite Prime Number Generator

I did something similar to this when I was learning about the many applications of sieving. At the time I could fit a sieve of size around 10^8 in memory, so sieving just odd numbers gives a quick algo for primes up to 2x10^8. Running two sieves, residue 1 and 5 mod 6 boosts performance by a factor ...
by yourmaths
Thu Dec 28, 2017 11:32 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 250
Replies: 14
Views: 3252

Re: Problem 250

I just solved 249 and 250. While 249 is probably easier to understand, 250 is (can be?!) definitely the easier problem computationally!
by yourmaths
Fri Dec 15, 2017 9:46 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 287
Replies: 14
Views: 3674

Re: Problem 287

Hmm... It seems like each encoding can refer to different images. For example, 011101010 could refer to both: ox xx as well as ooxx ooxx xxxx xxxx (here o represents white and x represents black squares). The larger image could be enforced by splitting one of the 2x2 squares but then that encoding c...
by yourmaths
Fri Nov 17, 2017 8:52 am
Forum: News, Suggestions, and FAQ
Topic: Solution thread
Replies: 8
Views: 1217

Re: Solution thread

Personally I think the solutions forums are the best part of PE (apart from the problems of course!). One of the most exciting things on this site is seeing a variety of approaches to solving any particular problem; some problems really only have one solution but many problems have many different wa...
by yourmaths
Tue Nov 14, 2017 11:00 pm
Forum: Recreational
Topic: Solving PE problems multiple times.
Replies: 7
Views: 3888

Re: Solving PE problems multiple times.

Haha! I have wasted enough time solving problems once to consider starting again!
by yourmaths
Sat Jun 17, 2017 10:40 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 606
Replies: 8
Views: 1809

Re: Problem 606

I am in a similar position with this problem. I've worked out the formula for the answer, and even a semi-smart way of calculating it without generating massive amounts of primes, but my estimate for the calculation time needed is still ~1000 hrs. My rule of thumb is that if I find myself needing to...
by yourmaths
Sat Jun 03, 2017 6:22 am
Forum: Number Theory
Topic: Project Euler Factoring Challenge
Replies: 4
Views: 4576

Re: Project Euler Factoring Challenge

Here are some 1-minute benchmarks from different methods I've tried: Trial factoring can factor 18 digits in less than one minute, but quickly becomes infeasible. The continued fraction method is a good way to get into the more complex methods. With CF I can factor the 34-digit number in 1 minute. I...
by yourmaths
Thu Mar 23, 2017 7:43 am
Forum: Number Theory
Topic: Project Euler Factoring Challenge
Replies: 4
Views: 4576

Project Euler Factoring Challenge

As far as I'm aware there's no problems in Project Euler that require us to factor really big numbers. And yet, some of the more recent factorisation algorithms are really fascinating! So here it is - The Project Euler Factoring Challenge: pefc=[6, 21, 781, 1081, 31747, 312017, 3180883, 53011019, 42...
by yourmaths
Tue Feb 14, 2017 11:14 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 590
Replies: 2
Views: 685

Re: Problem 590

OK thanks sjhillier. At least I'm on the right track now (I think!).

It seems like 'the least common multiple of the integers in the set' is still somewhat ambiguous for the same reason, until the lcm of three numbers is defined.
by yourmaths
Tue Feb 14, 2017 10:11 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 590
Replies: 2
Views: 685

Problem 590

I haven't been able to find a satisfactory definition of the lcm of a set in my usual references. Just to be clear, I assume that lcm(a,b,c) = lcm(a,lcm(b,c)), so that lcm(2,3,5) = 30. An alternative definition (probably wrong) of lcm of a set might be the maximum lcm of elements taken pair-wise, in...