Problem 308

kingvash · Post by **kingvash** » Mon Nov 01, 2010 3:03 am

I am having difficulty counting the number of iterations (it may be just a fence post problem).

Could anyone confirm that it takes takes:
19 iterations to produce 2 ^ 2
36980 iterations to produce 2 ^ 29
73886466 iterations to produce 2 ^ 379

Thanks.

sivakd · Post by **sivakd** » Mon Nov 01, 2010 3:10 am

I haven't solved it yet. I have a basic algorithm that can generate the primes but it would take a lot of time to find the answer being asked. In your case, the first one is correct. But the remaining two are off by 1.

Edit: I can now confirm my above statement after solving this problem.

dstrower · Post by **dstrower** » Thu Jan 20, 2011 9:21 pm

Did you have any difficulty in getting the program to run in under a minute?

raggie · Post by **raggie** » Tue Feb 22, 2011 10:37 pm

Is an unsigned 32 (or 64) bit integer enough to store the answer?

hk · Post by hk » Wed Feb 23, 2011 10:17 am

32: no. 64: yes.

Oliver1978 · Post by **Oliver1978** » Thu Jul 19, 2018 3:27 pm

There seem to exist two valid versions. Version A takes 707 steps to find 2^7, Version B takes 710 steps.

On which of those does the correct solution rely?

kenbrooker · Post by **kenbrooker** » Thu Jul 19, 2018 5:23 pm

I vote for 710...

Oliver1978 · Post by **Oliver1978** » Thu Jul 19, 2018 7:39 pm

Is that vote because you've already solved this? Or just a guess...

kenbrooker · Post by **kenbrooker** » Thu Jul 19, 2018 11:10 pm

Solved, but you never know...

Oliver1978 · Post by **Oliver1978** » Thu Jul 19, 2018 11:32 pm

Apparently it's the slow branch then. Thanks

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