Search found 22 matches

by yourmaths
Wed Nov 14, 2018 9:45 am
Forum: Clarifications on Project Euler Problems
Topic: Problem 521
Replies: 9
Views: 2313

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: 3
Views: 1829

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: 12
Views: 3929

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: 12
Views: 3929

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: 10
Views: 2272

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: 861

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: 861

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: 1189

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: 12
Views: 2482

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: 3323

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: 789

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: 1956

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: 1598

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: 3
Views: 1829

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: 3
Views: 1829

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: 520

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: 520

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...
by yourmaths
Wed May 18, 2016 1:48 am
Forum: Clarifications on Project Euler Problems
Topic: Problem 144
Replies: 19
Views: 6006

Re: Problem 144

mpiotte wrote:
grump wrote:Doesn't the laser beam get reflected off the top before it ever makes it into the ellipse?
The light beam enters through the gap at x ~ 0.0071 (-0.01 <= 0.0071 <= 0.01).
Wouldn't it be great if just once there was a trick question as alluded to here with the answer equal to 0?
by yourmaths
Thu Mar 03, 2016 7:06 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 516
Replies: 5
Views: 2201

Re: Problem 516

rakeshp wrote:is
S(1000000)=2236471777
S(1000000000)=964002218
correct?
I'm getting close to a solution on this.

For those who might use these numbers to check their method, it might save some time to point out that these two answers are actually mod 2^32, rather than S(L) itself.
by yourmaths
Tue Aug 04, 2015 10:04 am
Forum: News, Suggestions, and FAQ
Topic: PE has been hacked (02/08/2015 00:42 CEST)
Replies: 36
Views: 8567

Re: PE has been hacked (02/08/2015 00:42 CEST)

Like the rest of you, I'm struggling to understand the logic of hacking PE.

Why not demonstrate how good you are at computers by... I don't know... maybe solving as many PE problems as possible?