Project Euler Forum

Apoplogies for posting on a relatively old problem but I've only recently discovered the site. Could anyone provide some feedback on problem 120. I thought I had a suitable algorithm which correctly calculates the a = 7, rmax = 42 example provided. However my total is incorrect. Hoping this doesn't breach your guidelines re-solutions, could anyone confirm that these early values are correct:
a = 3 rmax = 6
a = 4 rmax = 8
a = 5 rmax = 10
a = 6 rmax = 12
a = 7 rmax = 42
a = 8 rmax = 48
a = 9 rmax = 54
a = 10 rmax = 60
a = 11 rmax = 110
a = 12 rmax = 120
a = 13 rmax = 130
a = 14 rmax = 140
a = 15 rmax = 210

5⁵+7⁵ [cong] 24 (mod 36).

Thanks that helped. Solved now.

what's the range that the n value can have??

what's this question asking exactly?

is it asking for the sum of all the rmax values for a in range2<a<1001

so 6 + 8 + 10 + 24 + 42 + 48....until it reaches the rmax for a=100?

SJ_Mufasa wrote:what's the range that the n value can have??

None is specified by the problem, so n can take any (positive) integer value.

what's this question asking exactly?
is it asking for the sum of all the rmax values for a in range2<a<1001
so 6 + 8 + 10 + 24 + 42 + 48....until it reaches the rmax for a=100?

Yes, up to a=1000.

oh, thanks very much, finally solved now =]

need help

is this true
when
a=5; rmax=20 when n=7
?
looking at previous posts it doesn't look promising both showing 10

its late maybe me being dumb

p.s can this problem be done in ULL range?
sorry mean 64bit int range

frogboy77 wrote:a=5; rmax=20 when n=7

Correct.

frogboy77 wrote:p.s can this problem be done in ULL range?
sorry mean 64bit int range

It can quite comfortably be done in 32 bit range too.

I'm kinda struggling with how to describe an error without hinting at how the problem should be solved...

But the answer which project euler takes as correct one assumes that the maximum remainder for, say, a = 705 is r = 496320. In fact, it's 494910.

Please, check.

You are not supposed to create new threads about a problem. You probably didn't know this cause you're new, but please post your problem in this thread: Problem 120. If you have a problem on a problem, search the forum for "Problem xxx", where xxx is the problem number. There will already be an existing thread there.

An admin will probably delete this thread or something.

Also, the answers to problems are never wrong. Problem 120 can be solved through analysis. I solved it through pen/paper, didn't even need a program!

oleglyamin wrote:I'm kinda struggling with how to describe an error without hinting at how the problem should be solved...

But the answer which project euler takes as correct one assumes that the maximum remainder for, say, a = 705 is r = 496320. In fact, it's 494910.

Please, check.

From the Project Euler about page: Or to put it more clear:
if about 4400 people have solved this problem, do you think they all solved it wrong?
Don't you think we would have been told the answer was wrong much and much earlier?

Thanks for replying. I pm-ed you.

Error's been found. It was my math.

Issue already solved.

@mdenhoed Please don't create a new thread for a problem if one already exists.

bobfin wrote: Thu Oct 22, 2009 10:06 pm Apoplogies for posting on a relatively old problem but I've only recently discovered the site. Could anyone provide some feedback on problem 120. I thought I had a suitable algorithm which correctly calculates the a = 7, rmax = 42 example provided. However my total is incorrect. Hoping this doesn't breach your guidelines re-solutions, could anyone confirm that these early values are correct:
a = 3 rmax = 6
a = 4 rmax = 8
a = 5 rmax = 10
a = 6 rmax = 12
a = 7 rmax = 42
a = 8 rmax = 48
a = 9 rmax = 54
a = 10 rmax = 60
a = 11 rmax = 110
a = 12 rmax = 120
a = 13 rmax = 130
a = 14 rmax = 140
a = 15 rmax = 210

jaap wrote: Sat Sep 25, 2010 2:42 am

frogboy77 wrote:a=5; rmax=20 when n=7

Correct.

frogboy77 wrote:p.s can this problem be done in ULL range?
sorry mean 64bit int range

It can quite comfortably be done in 32 bit range too.

How can a=5; rmax=10 and a=5;rmax=20 both be correct?

Only one is correct...

I started with the problems just recently and use it to learn different programming languages. But I'm posting a question on this problem that is bugging me. For example, one of the above entries has, for a=9, max = 60. That is true for n = 3, but for n=9 it is 80. What am I missing, in particular since n is not bounded (yes the entries will repeat eventually due to the modulus)? Clarification would be much appreciated.

rmax does not equal 60 when n=3...