@@ -10,6 +10,12 @@ defmodule Whales do
1010
1111 def distance_to ( a , b ) , do: abs ( a - b )
1212
13+ def increasing_distance_to ( a , b ) do
14+ 1 .. abs ( a - b )
15+ |> Enum . to_list ( )
16+ |> Enum . sum ( )
17+ end
18+ 1319 def find_cheapest_route ( positions ) ,
1420 do: find_cheapest_route ( positions , Enum . min ( positions ) , nil )
1521
@@ -37,6 +43,37 @@ defmodule Whales do
3743 end
3844 end
3945
46+ def find_new_cheapest_route ( positions ) ,
47+ do: find_new_cheapest_route ( positions , Enum . min ( positions ) , nil )
48+ 49+ def find_new_cheapest_route ( positions , target , cheapest ) do
50+ # This takes a while, so we add debug output
51+ IO . inspect ( target , label: "Target" )
52+ IO . inspect ( Enum . count ( positions ) , label: "Positions" )
53+ 54+ if target >= Enum . count ( positions ) + 1 do
55+ cheapest
56+ else
57+ current =
58+ if target == Enum . max ( positions ) + 1 do
59+ cheapest
60+ else
61+ positions
62+ |> Enum . map ( fn position -> increasing_distance_to ( position , target ) end )
63+ |> Enum . sum ( )
64+ end
65+ 66+ new_cheapest =
67+ if current < cheapest do
68+ current
69+ else
70+ cheapest
71+ end
72+ 73+ find_new_cheapest_route ( positions , target + 1 , new_cheapest )
74+ end
75+ end
76+ 4077 @ spec first ( ) :: Integer
4178 def first ( ) do
4279 positions = load_file ( "../input.txt" )
@@ -45,6 +82,8 @@ defmodule Whales do
4582
4683 @ spec second ( ) :: Integer
4784 def second ( ) do
85+ positions = load_file ( "../input.txt" )
86+ find_new_cheapest_route ( positions )
4887 end
4988end
5089
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