Search found 68 matches

by RobertStanforth
Thu May 10, 2018 3:58 pm
Forum: Clarifications on Project Euler Problems
Topic: problem 206
Replies: 33
Views: 16307

Re: problem 206

1928374655647382910 is not a perfect square.
by RobertStanforth
Thu May 10, 2018 3:50 pm
Forum: Clarifications on Project Euler Problems
Topic: problem 206
Replies: 33
Views: 16307

Re: problem 206

@thechosenone98: I have moved your post to the correct forum for problem clarifications. Also, please do not post answers in public view !!! I have removed it from your post. To answer your question, 1388659302 is not a valid solution. The value you give for its square is not correct, and is not eve...
by RobertStanforth
Mon May 07, 2018 2:10 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 023
Replies: 56
Views: 27836

Re: Problem 023

Dear Liad777, I have moved your post to the existing thread for this problem. In general, the "Problem xxx" naming convention (with leading zeros) in this forum means it should be possible to find such threads where they already exist. As for your question, 28123 is merely an upper bound t...
by RobertStanforth
Wed May 02, 2018 7:26 pm
Forum: Recreational
Topic: why are hints for solutions not allowed?
Replies: 2
Views: 7876

Re: why are hints for solutions not allowed?

Project Euler's approach has always been "If you can't solve it, you can't solve it", which is why PE does not provide an open forum for discussing solution methods.

You may be interested in this thread, in which a tangentially related point was discussed.
by RobertStanforth
Sat Apr 28, 2018 1:25 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 352
Replies: 35
Views: 17088

Re: Problem 352

@hamsterofdeath: I sent you a PM.
by RobertStanforth
Fri Apr 27, 2018 7:16 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 493
Replies: 5
Views: 4179

Re: Problem 493

This is indeed the correct forum for discussing issues with understanding the wording of a problem. The problem only talks about the number of distinct colours in the draw. So, whether the balls have any other distinguishing marks (aside from their colour) is irrelevant. The order of the draw (and w...
by RobertStanforth
Wed Apr 18, 2018 7:32 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 064
Replies: 24
Views: 12400

Re: Problem 064

Dear Omri_Shavit,
I moved your post to the existing clarification thread for this problem.
Based on your workings for the first 13 cases, you understand the problem statement correctly.
Moreover, the continued fraction you provided for 9999 was correct - but your overall answer was much too low.
by RobertStanforth
Thu Apr 05, 2018 7:24 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 141
Replies: 27
Views: 15960

Re: Problem 141

Oliver1978 wrote: Thu Apr 05, 2018 6:47 pm My thoughts concerning the sample numbers from the description: 9 is in the list because with d=2 we get q=4, r=1. For this [1,2,4] there's the factor 2 forming this geometric sequence.

Am I right with this? Or am I completely going wrong?
Yes, you are correct.
by RobertStanforth
Thu Mar 29, 2018 8:07 am
Forum: Clarifications on Project Euler Problems
Topic: Problem 623
Replies: 18
Views: 6730

Re: Problem 623

With regard to the earlier comments in this thread about characters versus symbols for variable names, the problem description has now been amended to specify that a variable is a single letter (drawn from an infinite alphabet). This does not change the answer but should avoid some confusion. Thank ...
by RobertStanforth
Mon Mar 26, 2018 10:57 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 623
Replies: 18
Views: 6730

Re: Problem 623

Also, $\Lambda(n)$ is described as the number of distinct $\alpha$-equivalent lambda-terms that can be written using at most $n$ symbols, but it's actually the number of such symbols which are closed . Thank you for pointing that out, Sardaai. The description has now been updated to ask for closed ...
by RobertStanforth
Thu Mar 08, 2018 6:36 pm
Forum: Programming languages
Topic: New Preferred Programming Language Requests
Replies: 170
Views: 120559

Re: Add jq to the language drop-down in the forums?

Hi I just answered my first problem and I am planning to answer all problems in jq -- https://stedolan.github.io/jq/ I was wondering if there were any plans to add jq to the dropdown for picking my default language. I've left it blank for now which works fine but it would be cool to be able to spec...
by RobertStanforth
Mon Mar 05, 2018 7:29 am
Forum: Clarifications on Project Euler Problems
Topic: Problem 620
Replies: 20
Views: 8769

Re: Problem 620

I would post some digits or some additional data points that my program is giving me beyond G(20) = 205, but with still fewer than 100 solvers, I am worried that some would feel that it is too soon to post additional information. Is anyone willing to let me PM them some numbers so you can tell me i...
by RobertStanforth
Tue Feb 27, 2018 6:56 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 620
Replies: 20
Views: 8769

Re: Problem 620

The gears have a pitch (i.e. tooth-to-tooth distance) of 1cm. Hence a circle's circumference in centimetres is equal to its number of teeth when it's considered as a gear.
by RobertStanforth
Mon Feb 12, 2018 7:21 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 620
Replies: 20
Views: 8769

Re: Problem 620

abcwuhang wrote: Mon Feb 12, 2018 1:18 pm As an epicyclic gear train allows the planets to rotate, what is the meaning of perfectly meshing of gears? Could you show how to drive the whole system? Thanks.
Each of the six gears rotates about its own axis. The axes themselves don't move.
by RobertStanforth
Sun Feb 11, 2018 9:03 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 620
Replies: 20
Views: 8769

Re: Problem 620

Radewoosh wrote: Sun Feb 11, 2018 6:42 pm Can two planets (with this same circumference) have exactly the same position?
No, the four planets must all be distinct: no two may have the same size and position.
by RobertStanforth
Sun Feb 11, 2018 3:24 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 620
Replies: 20
Views: 8769

Re: Problem 620

Rotations and reflections do not give rise to distinct arrangements.
by RobertStanforth
Sun Feb 11, 2018 1:34 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 620
Replies: 20
Views: 8769

Re: Problem 620

Hi Albert,

The 'planet' gears can overlap if they occupy different locations in the $z$ axis (i.e. the direction coming out of the page).
by RobertStanforth
Mon Jan 22, 2018 9:21 am
Forum: Recreational
Topic: Winning Lottery with Prime Number!?
Replies: 8
Views: 13160

Re: Winning Lottery with Prime Number!?

I believe the book that jimfan refers to is "From Here to Infinity" by Ian Stewart.
by RobertStanforth
Wed Nov 29, 2017 7:10 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 323
Replies: 4
Views: 3455

Re: Problem 323

Yes, but that happens with probability 0, so that case will not affect the expected value of $N$. If the sequence $y_i$ is truly random isn't there a chance, albeit very slim, that any single bit remains 0 for $N=\infty$? reaching $x_i = 2^{32}-1$ is not an eventuality unless each 32-bit integer can...
by RobertStanforth
Fri Oct 20, 2017 8:12 am
Forum: Clarifications on Project Euler Problems
Topic: Problem 276
Replies: 31
Views: 13349

Re: Problem 276

SteveB wrote: Fri Oct 20, 2017 6:48 am Am I allowed to ask - can this problem be solved in O(n^2) time or is it sometime better?
Each Project Euler problem can be solved within a minute, on a reasonably powered home computer. That should provide you with an indication of whether a faster algorithm exists.