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|
pairings =
File.stream!("inputs/day13.txt")
|> Enum.reduce(%{}, fn line, acc ->
[_, from, dir, amount, to] =
Regex.run(
~r/^(\w+) would (gain|lose) (\d+) happiness units by sitting next to (\w+)./,
line
)
{amount, ""} = Integer.parse(amount)
amount =
if dir == "lose" do
-amount
else
+amount
end
{_, newAcc} =
Map.get_and_update(acc, from, fn
nil -> {nil, %{to => amount}}
existing -> {existing, Map.put(existing, to, amount)}
end)
newAcc
end)
defmodule A do
def permutations([lastElement]) do
[[lastElement]]
end
def permutations(list) do
Enum.flat_map(list, fn start ->
rest = List.delete(list, start)
Enum.map(permutations(rest), fn perm ->
[start | perm]
end)
end)
end
def maxHappiness(pairings, people) do
A.permutations(people)
|> Enum.map(fn tableSorting ->
offsetSorting = Stream.cycle(tableSorting) |> Stream.drop(1)
Enum.zip(tableSorting, offsetSorting)
|> Enum.map(fn {p1, p2} ->
oneToTwo = Map.get(pairings, p1, %{}) |> Map.get(p2, 0)
twoToOne = Map.get(pairings, p2, %{}) |> Map.get(p1, 0)
oneToTwo + twoToOne
end)
|> Enum.sum()
end)
|> Enum.max()
end
end
maxHappinessWithoutMe = A.maxHappiness(pairings, Map.keys(pairings))
IO.puts("Maximum happiness without me: #{maxHappinessWithoutMe}")
maxHappinessWithMe = A.maxHappiness(pairings, ["Me" | Map.keys(pairings)])
IO.puts("Maximum happiness with me: #{maxHappinessWithMe}")
|
