Most likely O^3

Oh, O(n^k) isn't so bad. Sure, it's a bit slow, but for reasonable values of n the process *will* finish. I presume this is only being run once per user, though n will be the number of users, which could be a bit on the high side. Still... might not be too bad. Computers are pretty fast these days.

OTOH, the other day I wrote a script that was horrible. I knew it was brute force when I wrote it, but I only needed to run it a couple of times, and n was never going to exceed 15 or so, so I didn't worry about efficiency. For n=3 it ran fine. Took a minute, but I knew it was an inefficient implementation. So I set n to 4...

Some of you may know where this is going. Windows Me told me I was running low on disk space, so I stopped the process and discovered that the swapfile was over 180GB. (It was a recursive algorithm...) So I analysed the algorithm, and it turned out that it was approximately O((n^2)!), and using an amount of RAM proportional to running time. Yeah, that's a factorial. Guess I have to come up with a slightly more clever algorithm. 

$;=sub{$/};@;=map{my($a,$b)=($_,$;);$;=sub{$a.$b->()}}
split//,".rekcah lreP rehtona tsuJ";$\=$ ;->();print$/

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In reply to Re: Identifying fraudulent users, by comparing values in database. with a hash..? by jonadab
in thread Identifying fraudulent users, by comparing values in database. with a hash..? by vili

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