In my opinion, this was the easiest problem so far. The brute-force method is easy to implement and runs very fast.
This is the code:
$fraction = '' 1.upto(1000000) do |i| $fraction << i.to_s end def d_(n) $fraction[n-1].to_i end puts d_(1) * d_(10) * d_(100) * d_(1000) * d_(10000) * d_(100000) * d_(1000000)
It runs in slightly lesser than one second.
The last line isn’t very Ruby-ish because I copied it from the problem description page, because I’m too lazy to write it myself. That’s also why I have a d_(n) function.
Tags: project euler, ruby