80 lines
3.6 KiB
Erlang
80 lines
3.6 KiB
Erlang
|
-module(day24).
|
||
|
|
-export([start/0]).
|
||
|
|
|
||
|
|
read_input(Filename)
|
||
|
|
-> { ok, Input } = file:read_file(Filename),
|
||
|
|
lists:map(fun(X) ->
|
||
|
|
[A,B|_] = re:split(X, "/"),
|
||
|
|
{ AInt, _ } = string:to_integer(A),
|
||
|
|
{ BInt, _ } = string:to_integer(B),
|
||
|
|
{ AInt, BInt }
|
||
|
|
end, re:split(string:chomp(Input), "\n")).
|
||
|
|
|
||
|
|
strongest_bridge(Input)
|
||
|
|
-> strongest_bridge(Input, 0, 0, []).
|
||
|
|
|
||
|
|
strongest_bridge([], _LastEdge, Sum, Train)
|
||
|
|
-> { Sum, Train };
|
||
|
|
strongest_bridge(Input, LastEdge, Sum, Train)
|
||
|
|
-> { Matching, _ } = lists:partition(fun(X) ->
|
||
|
|
{ A, B } = X,
|
||
|
|
(A == LastEdge) or (B == LastEdge)
|
||
|
|
end, Input),
|
||
|
|
if length(Matching) == 0 -> { Sum, Train };
|
||
|
|
true ->
|
||
|
|
MatchingSums = lists:map(fun(X) ->
|
||
|
|
{ _, Remaining } = lists:partition(fun(Y) -> Y == X end, Input),
|
||
|
|
{ A, B } = X,
|
||
|
|
NewTrain = lists:append(Train, [X]),
|
||
|
|
NewSum = Sum + A + B,
|
||
|
|
if A == LastEdge -> strongest_bridge(Remaining, B, NewSum, NewTrain);
|
||
|
|
true -> strongest_bridge(Remaining, A, NewSum, NewTrain)
|
||
|
|
end
|
||
|
|
end, Matching),
|
||
|
|
[FirstSum|_] = lists:sort(fun(X, Y) ->
|
||
|
|
{ A, _ } = X,
|
||
|
|
{ B, _ } = Y,
|
||
|
|
B =< A
|
||
|
|
end, MatchingSums),
|
||
|
|
FirstSum
|
||
|
|
end.
|
||
|
|
|
||
|
|
longest_bridge(Input)
|
||
|
|
-> longest_bridge(Input, 0, 0, []).
|
||
|
|
|
||
|
|
longest_bridge([], _LastEdge, Sum, Train)
|
||
|
|
-> { Sum, Train };
|
||
|
|
longest_bridge(Input, LastEdge, Sum, Train)
|
||
|
|
-> { Matching, _ } = lists:partition(fun(X) ->
|
||
|
|
{ A, B } = X,
|
||
|
|
(A == LastEdge) or (B == LastEdge)
|
||
|
|
end, Input),
|
||
|
|
if length(Matching) == 0 -> { Sum, Train };
|
||
|
|
true ->
|
||
|
|
MatchingSums = lists:map(fun(X) ->
|
||
|
|
{ _, Remaining } = lists:partition(fun(Y) -> Y == X end, Input),
|
||
|
|
{ A, B } = X,
|
||
|
|
NewTrain = lists:append(Train, [X]),
|
||
|
|
NewSum = Sum + A + B,
|
||
|
|
if A == LastEdge -> longest_bridge(Remaining, B, NewSum, NewTrain);
|
||
|
|
true -> longest_bridge(Remaining, A, NewSum, NewTrain)
|
||
|
|
end
|
||
|
|
end, Matching),
|
||
|
|
[FirstSum|_] = lists:sort(fun(X, Y) ->
|
||
|
|
{ A, I } = X,
|
||
|
|
{ B, J } = Y,
|
||
|
|
if length(I) == length(J) -> B =< A;
|
||
|
|
true -> length(J) =< length(I)
|
||
|
|
end
|
||
|
|
end, MatchingSums),
|
||
|
|
FirstSum
|
||
|
|
end.
|
||
|
|
|
||
|
|
start()
|
||
|
|
-> SampleInput = read_input("sample"),
|
||
|
|
io:fwrite("~p~n", [strongest_bridge(SampleInput)]),
|
||
|
|
io:fwrite("~p~n", [longest_bridge(SampleInput)]),
|
||
|
|
ProblemInput = read_input("problem"),
|
||
|
|
io:fwrite("~p~n", [strongest_bridge(ProblemInput)]),
|
||
|
|
io:fwrite("~p~n", [longest_bridge(ProblemInput)]).
|