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Re^2: Triangle Numbers Revisited

by Limbic~Region (Chancellor)
on Oct 14, 2004 at 12:53 UTC ( #399187=note: print w/replies, xml ) Need Help??

in reply to Re: Triangle Numbers Revisited
in thread Triangle Numbers Revisited

Good catch! I didn't have time to track it down myself this morning as I was supposed to be getting ready for work. For the purposes of the original thread, it appears that 0 was being allowed as a triangular number. With that allowance, all numbers can indeed be the sum of 3 triangles.

As far as speed, you are right that this is quite fast. If it was not fast enough in a real problem you would likely use C as tachyon, the cheater, did ;-)
I have no idea about how to figure out the big O of either solution, but I did want to mention that my solution is more than a constant factor faster in case you decided to spend the time optimizing. At 5_000 random targets between 1 and 5_000_000 it was twice as fast, but for 10_000 random targets between 1 and 987_654_321 it was three times as fast. I didn't want to come off as offensive - I just like silly challenges like this.

Cheers - L~R

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