Project Euler Forum

Problem 332 (View Problem)

I don't understand what is meant by integer coordinates on the surface. If the radius is r, does that mean that there are points 0 to r going from equator to pole?

EDIT: Okay, I think I get it. The center is 0, 0, 0. A Point(x, y, z) is on the surface, if x, y and z <= r and that coordinate is actually distance r away from Point(0, 0, 0). Is that correct?

LarryBlake wrote:Is that correct?

Yep, the point (x,y,z) must be on the surface of the sphere and its coordinates (i.e. x, y and z) must be integers.

I can't seem to get the right answer for this problem even though I get the right value of A(14). I've looked over my algorithm several times, and I'm wondering if there's some precision issue going on (although, it seems unlikely since there aren't that many operations, so I'm really puzzled). Can someone please check if these 3 arbitrarily selected values of A(r) look correct? (I hope this is OK; you need 50 of them to compute the final answer, and these aren't like the most "difficult" cases or anything AFAICT).
A(5) = 2.724572812036574
A(27) = 0.07520891357997117
A(30) = 0.5607476454096538
EDIT: Ahhh never mind, I found a stupid bug in the computation.

jun0 wrote:I can't seem to get the right answer for this problem even though I get the right value of A(14).

I'm in that situation now. My answers match those given above as well as A(14).

Can I PM my values for A(1..50) to someone who has solved it?

Edit: 6 weeks later, I had the idea to check my answers for even r against those for r/2, and I found my own stupid bug.