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