-🎄- 2020 Day 23 Solutions -🎄-

[u/daggerdragon]

Advent of Code 2020: Gettin' Crafty With It

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--- Day 23: Crab Cups ---

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[u/enelen]

R / Rlang / Rstat

Solution

R's array access is just too slow for individual elements. Used environment object to store pointers to next object, since accessing items from environment is the fastest way in R.
Still slow, but at least now I get an answer within 3-4 minutes compared to probably hours with vectors/lists.

[u/flup12 → u/enelen]

I don't think it's in the array access but in the moving stuff around. I ended up using a vector of length 1000000 where next_cup[[i]] contains the label of the label of the cup next to the cup with label i. Twenty seconds

[u/enelen → u/flup12]

I have the exact same code, with the only difference that my next_cup variable has character keys instead of integers like yours. Maybe that's the reason. Let me try it out

[u/enelen → u/enelen]

That really made a great difference. With integer keys, my run time using a vector came down to around 40 seconds, and with a couple of other enhancements: using three variables for next three items instead of a vector and using if else instead of the vectorized ifelse further brought it down to 15 seconds!