Project Euler Forum

hk wrote: ↑Fri May 08, 2020 9:28 am There's actually no need to have looked up the answer somwhere.
Some people simply try some answers around the value their program gives. Just to rule out off by one answers.

Never thought of that

I've looked through the thread and that answers about the ace but i still cant work out why im off by one. Is there any chance i could PM you a list of my results for each pair of hands and you let me know which one is wrong? Sure. But how do you know you're one off if you haven't solved it yet? Al...

Hi all,
I'm going slightly mad here: fairly sure my algorithm is right (gives 902212330695 for sqrt(4850) anyway), but can't seem to get the right answer. Any volunteers for a PM to validate my method and/or some other examples?
Cheers,
Claude

Tiny point this, but one that might be useful for some: would it be possible to use thousands separators in the questions. I'm sure I'm not alone in finding 'mod 10'000'007' more readable that the amalgamed '10000007' - ...
Cheers,
Claude

Right, got there in the end, although the program takes about 40 seconds to come up with the answer...
Thanks for the help again!
Claude

Right, back to the drawing board then ...
Thanks for getting back though!

Hi all, Could I ask for two pieces of input here: 1) D(13) is a 5-digit figure starting with a 4 and ending in an even digit - is that correct? 2) I'm using float values in C and my suspicion is that my solutions turns out wrong because of a precision issue. I've tried (long) double but the result i...

Thanks for your quick response, jaap. And thanks also for the offer of a PM conversation. I won't bother you just yet as I've actually only got three pairs so clearly there's something massively wrong with my approach. Back to the drawing board then. Cheers, Claude ******** EDIT 10 minutes later: No...

Hello all, I know that quite some folk have solved this one already and it doesn't look too daunting, really - except that: well I'm getting 186 and not 184 as result for F_3(100). Is that a typo that has been missed because people have gone straight on to the grown-up stuff with Sigma_k F_k(10^3) -...

Blimey, got there in the end - and I can't believe how long I spent looking at the code when it turned out to be basically sound and my mistake was somewhere entirely else... I know see why so many people seem to be getting the same false result as I did: and to all my bothers and sisters out there ...

Nothing particularly interesting to say, other than that I'm one of those who get the 'classic but wrong' answer for 10^10 as well even though the answer for 38000000 is correct.
So if, as I rather expect, I end up going completely mad over this one, please come and visit me at the hospital
DeKlod

Can I just add another voice to the call for a slight clarification on this problem: I feel that instead of asking for how many solutions there are for 1<=n<=9, it would be clearer of the question asked for the sum of s(n) where s(n) stands for the number of solutions for a particular value of n... ...

Thanks for that, jaap! Just one last question, if I may: is there any other obvious technique if you really need large quantities of data? Imagine a sieve for primes up to - say - 10^12. Vectors of type bool seem to be fine up to about 10^10 but not further. So I guess that's where you need to chang...

Cheers Jaap, I'm afraid I'll have to confess my ignorance on the first question (I'll google that though). I do use vectors, yes, but I would have thought it would pose problems of efficiency too as it will take up a lot of memory. I'll try that approach over the weekend though and see what happens ...

Hello all, Maybe someone could enlighten me on this one: the PDF solution sheet for this problem describes several possible algorithms of varying efficiency, yet they mainly seem to rely on an array containing all the required integer values, i.e. 10^8 numbers in this case. On my system and using C/...

Hi all, I was wondering whether someone would be good enough to check the following values for me (all given modulo 1'000'000'007): P(1000) = Values removed by moderator P(10'000) = P(100'000) = P(1'000'000) = P(10'000'000) = Thanks in advance! Claude EDIT: Disregard this, everyone... I missed a mod...

Well, this one is still haunting me. I now get a total of 3***626 unique lines.
Could someone check whether this seems correct (and if not possibly let me know the last couple of digits so I'll know when I'm approaching the answer - or would that already be a form of cheating?)
Cheers,
Claude

Thanks Animus, I'll have another look at that bit then

Hi all,
Problem 630 has been driving me up the wall for a few days now - I'm sure I'm missing something really stupid but I can't figure it out yet.
Could someone perhaps confirm that I've at least got the correct number of (unique) lines: I get 3***890...
Cheers,
Claude