# Day 4: Ceres Search
```elixir
Mix.install([:kino])
input = Kino.Input.textarea("Please paste your input:")
```
## Part 1
[](https://livebook.dev/run?url=https%3A%2F%2Fgithub.com%2Fnallwhy%2Fadvent-of-code%2Fblob%2Fmain%2F2024%2Fday_04.livemd)
https://adventofcode.com/2024/day/4
```elixir
data =
input
|> Kino.Input.read()
|> String.split("\n", trim: true)
```
```elixir
pos_char_map =
data
|> Enum.with_index()
|> Enum.flat_map(fn {line, y} ->
line
|> String.codepoints()
|> Enum.with_index()
|> Enum.map(fn {char, x} ->
{{x, y}, char}
end)
end)
|> Map.new()
directions = for x <- -1..1, y <- -1..1, {x, y} != {0, 0}, do: {x, y}
move_pos_fun = fn {pos_x, pos_y}, {direction_x, direction_y} ->
{pos_x + direction_x, pos_y + direction_y}
end
next_char_fun = fn
"X" -> "M"
"M" -> "A"
"A" -> "S"
_ -> nil
end
do_count_xmas_fun = fn
{_pos, "S"}, "S", _direction, _recur_fun ->
1
{pos, char}, char, direction, recur_fun ->
next_pos = move_pos_fun.(pos, direction)
next_char = pos_char_map[next_pos]
recur_fun.({next_pos, next_char}, next_char_fun.(char), direction, recur_fun)
_, _, _, _ ->
0
end
count_xmas_fun = fn
pos ->
case pos_char_map[pos] do
"X" ->
directions
|> Enum.map(fn direction ->
do_count_xmas_fun.({pos, "X"}, "X", direction, do_count_xmas_fun)
end)
|> Enum.sum()
_ ->
0
end
end
pos_char_map
|> Enum.reduce(0, fn {pos, _}, acc ->
acc + count_xmas_fun.(pos)
end)
```
## Part 2
https://adventofcode.com/2024/day/4#part2
```elixir
direction_chars_list =
for x <- [1, -1], y <- [1, -1] do
[
{{x, y}, "M"},
{{-x, -y}, "S"}
]
end
check_x_mas_fun = fn pos, direction_chars ->
direction_chars
|> Enum.all?(fn {direction, char} ->
pos_char_map[move_pos_fun.(pos, direction)] == char
end)
end
count_x_mas_fun = fn
pos ->
case pos_char_map[pos] do
"A" ->
direction_chars_list
|> Enum.count(fn direction_chars ->
check_x_mas_fun.(pos, direction_chars)
end)
|> case do
2 -> 1
_ -> 0
end
_ ->
0
end
end
pos_char_map
|> Enum.reduce(0, fn {pos, _}, acc ->
acc + count_x_mas_fun.(pos)
end)
```
