day 15 part 2

Author: maco

2021/elixir/lib/advent_of_code/day_15.ex

@@ -3,31 +3,31 @@ defmodule AdventOfCode.Day15 do
     nodes = parse(args)
     |> Map.update({0,0}, nil, fn {v, dist} -> {v, 0} end)
 
-    target = get_target(nodes)
+    target = Map.keys(nodes) |> Enum.max()
 
     dijkstra(Map.delete(nodes, {0,0}), {{0,0}, nodes[{0,0}]}, target)
   end
 
-  def get_target(nodes) do
-    {{max_r, _}, _} = Enum.max_by(nodes, fn {{r, _c}, _} -> r end)
-    {{_, max_c}, _} = Enum.max_by(nodes, fn {{_r, c}, _} -> c end)
-
-    {max_r, max_c}
-  end
-
   def dijkstra(_unvisited, {{r, c}, {_, distance}}, {r, c}), do: distance
 
   def dijkstra(unvisited, {coord, {label, distance}}, target) do
+    IO.puts(Enum.count(unvisited))
     neighbors = get_neighbors(unvisited, coord)
-    |> Map.map(fn {_, {v, d}} ->
-      {v, min(distance + v, d)}
+    |> Map.map(fn
+      {_, {v, :infinity}} ->
+        {v, distance + v}
+      {_, {v, d}} ->
+        {v, min(distance + v, d)}
     end)
 
     updated_unvisited = update_distances(unvisited, neighbors)
 
-    next = Enum.min_by(updated_unvisited, fn {_, {_, d}}
-      -> d
-    end)
+    next = Enum.reject(updated_unvisited, fn
+      {_, {_, :infinity}} ->
+        true
+      _ -> false
+      end)
+      |> Enum.min_by(fn {_, {_, d}} -> d end)
 
     dijkstra(Map.delete(updated_unvisited, coord), next, target)
   end
@@ -47,6 +47,16 @@ defmodule AdventOfCode.Day15 do
   end
 
   def part2(args) do
+    initial = parse(args)
+
+    {max_row, max_col} = target = Map.keys(initial) |> Enum.max()
+
+    nodes = expand_board(initial, {max_row + 1, max_row + 1})
+    |> Map.update({0,0}, nil, fn {v, dist} -> {v, 0} end)
+
+    new_target = Map.keys(nodes) |> Enum.max()
+
+    dijkstra(Map.delete(nodes, {0,0}), {{0,0}, nodes[{0,0}]}, new_target)
   end
 
   def expand_board(board, {max_row, max_col}) do

2021/elixir/test/advent_of_code/day_15_test.exs

@@ -60,8 +60,7 @@ defmodule AdventOfCode.Day15Test do
     assert String.trim(result) == String.trim(expected)
   end
 
-  # @tag :skip
-  test "big board 1" do
+  test "small board expansion" do
     input = """
     234
     456
@@ -91,8 +90,7 @@ defmodule AdventOfCode.Day15Test do
     assert String.trim(result) == String.trim(expected)
   end
 
-  # @tag :skip
-  test "big board 2" do
+  test "sample board expansion" do
     input = """
     1163751742
     1381373672
@@ -159,17 +157,28 @@ defmodule AdventOfCode.Day15Test do
     67554889357866599146897761125791887223681299833479
     """
 
+
     expanded = parse(input) |> expand_board({10,10})
 
     result = capture_io(fn -> show_grid(expanded) end)
     assert String.trim(result) == String.trim(expected)
   end
 
-  @tag :skip
   test "part2" do
-    input = nil
+    input = """
+    1163751742
+    1381373672
+    2136511328
+    3694931569
+    7463417111
+    1319128137
+    1359912421
+    3125421639
+    1293138521
+    2311944581
+    """
     result = part2(input)
 
-    assert result
+    assert result == 315
   end
 end