Saturday, July 21, 2018

Project Euler #110 - 41 days spent on a problem

Project Euler Problem #110 is an extended version of #108. The latter can be solved with simple brute force code pretty quickly, but the former obviously defies such simple-minded approach. One should generalize #108 in order to solve #110.

I solved #108 in Jun 10 by brute force. I immediately started finding the general rule. It took me, however, about 40 (four zero) days in the end. Even though I haven't been on this problem 24/7 for the last 41 days, I must have attempted over 50 times in total.

I am proud of myself not having searched for any solution or hint in the mean time. There are other problems for which I spent 2~3 weeks to solve, but 41 days on #110 is definitely my personal record.

* Most of the 50 attempts were purely speculative (even without pen and paper). Not much progress with the brain-only attempts, so I decided to revise #108 code to rearrange and extend the result. That helped in the end; even with it I still had to spend another 2~3 days until finally figuring out the rule.

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