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advent-of-code/day17/day17.erl

23 lines
982 B
Erlang
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2017-12-17 23:30:12 -05:00
-module(day17).
-export([start/0]).
spin_the_lock(NextValue, SpinQueue, Index, _Steps)
when NextValue == 2018 -> lists:nth(Index + 1 rem 2018, SpinQueue);
spin_the_lock(NextValue, SpinQueue, Index, Steps)
-> NextPosition = (Index + Steps) rem NextValue,
{ First, Last } = lists:split(NextPosition, SpinQueue),
spin_the_lock(NextValue + 1, lists:append([First, [NextValue], Last]), NextPosition + 1, Steps).
spin_the_lock2(NextValue, ValAtOne, _Index, _Steps)
when NextValue == 50000001 -> ValAtOne;
spin_the_lock2(NextValue, ValAtOne, Index, Steps)
-> NextPosition = (Index + Steps) rem NextValue,
if NextPosition == 0 -> spin_the_lock2(NextValue + 1, NextValue, NextPosition + 1, Steps);
true -> spin_the_lock2(NextValue + 1, ValAtOne, NextPosition + 1, Steps)
end.
start()
-> io:fwrite("~p~n", [spin_the_lock(1, [0], 0, 3)]),
io:fwrite("~p~n", [spin_the_lock(1, [0], 0, 303)]),
io:fwrite("~p~n", [spin_the_lock2(1, 0, 0, 303)]).