<!-- livebook:{"hub_id":"team-weiz"} -->
# Day 6
## Section
```elixir
example = """
....#.....
.........#
..........
..#.......
.......#..
..........
.#..^.....
........#.
#.........
......#...
"""
```
```elixir
defmodule Day06 do
def part1(input) do
{start, map} = parse_input(input)
move(start, map, {0, -1}, [start])
|> Enum.uniq()
|> length()
end
def move(_, _map, :out, breads), do: breads
def move({x, y}, map, {xmove, ymove} = dir, breads) do
next = {x + xmove, y + ymove}
{next, dir, breads} =
case Map.get(map, next) do
"." -> {next, dir, [next | breads]}
"#" -> {{x, y}, next_dir(dir), breads}
nil -> {next, :out, breads}
end
move(next, map, dir, breads)
end
def parse_input(input) do
for {row, y} <- input |> String.split("\n", trim: true) |> Enum.with_index(),
{dot, x} <- row |> String.split("", trim: true) |> Enum.with_index(),
reduce: {nil, %{}} do
{start, map} ->
case dot do
"^" -> {{x, y}, Map.put(map, {x, y}, ".")}
dot -> {start, Map.put(map, {x, y}, dot)}
end
end
end
def next_dir({0, -1}), do: {1, 0}
def next_dir({1, 0}), do: {0, 1}
def next_dir({0, 1}), do: {-1, 0}
def next_dir({-1, 0}), do: {0, -1}
end
Day06.part1(example)
```
```elixir
defmodule Day06P2 do
def part2(input) do
{start, map} = parse_input(input)
for {position, "."} <- map,
position != start,
:loop == move(start, Map.put(map, position, "#"), {0, -1}, %{}),
reduce: 0 do
accu -> accu + 1
end
end
def move(_, _map, _, :loop), do: :loop
def move(_, _map, :out, _), do: :out
def move({x, y}, map, {xmove, ymove} = dir, turns) do
next = {x + xmove, y + ymove}
{next, dir, turns} =
case Map.get(map, next) do
"." -> {next, dir, turns}
"#" -> {{x, y}, next_dir(dir), check_turn(turns, {{x, y}, dir, next_dir(dir)})}
nil -> {next, :out, turns}
end
move(next, map, dir, turns)
end
def parse_input(input) do
for {row, y} <- input |> String.split("\n", trim: true) |> Enum.with_index(),
{dot, x} <- row |> String.split("", trim: true) |> Enum.with_index(),
reduce: {nil, %{}} do
{start, map} ->
case dot do
"^" -> {{x, y}, Map.put(map, {x, y}, ".")}
dot -> {start, Map.put(map, {x, y}, dot)}
end
end
end
def next_dir({0, -1}), do: {1, 0}
def next_dir({1, 0}), do: {0, 1}
def next_dir({0, 1}), do: {-1, 0}
def next_dir({-1, 0}), do: {0, -1}
def check_turn(turns, turn) do
if Map.has_key?(turns, turn) do
:loop
else
Map.put(turns, turn, true)
end
end
end
Day06P2.part2(example)
```
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