31 lines
1.1 KiB
Erlang
31 lines
1.1 KiB
Erlang
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-module(day1_part2).
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-export([main/0]).
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% Main entry point
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main() ->
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{ok, Content} = file:read_file("input.txt"),
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Lines = string:split(string:trim(Content), "\n", all),
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{List1, List2} = lists:foldl(fun parse_line/2, {[], []}, Lines),
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CountMap = build_count_map(List2),
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SimilarityScore = calculate_similarity_score(List1, CountMap),
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io:format("Result: ~p~n", [SimilarityScore]).
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% Parse a single line into two integers and accumulate them into lists
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parse_line(Line, {Acc1, Acc2}) ->
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[Str1, Str2] = string:split(string:trim(Line), " ", all),
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{Num1, _} = string:to_integer(Str1),
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{Num2, _} = string:to_integer(Str2),
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{[Num1 | Acc1], [Num2 | Acc2]}.
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% Build a map of counts for elements in List2
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build_count_map(List) ->
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lists:foldl(fun(Elem, Acc) ->
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maps:update_with(Elem, fun(Count) -> Count + 1 end, 1, Acc)
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end, #{}, List).
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% Calculate the total similarity score
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calculate_similarity_score(List1, CountMap) ->
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lists:foldl(fun(Elem, Acc) ->
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Acc + Elem * maps:get(Elem, CountMap, 0)
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end, 0, List1).
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