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fix: Correct MASAS pattern detection in Day04 grid search

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fix: Refactor X-MAS pattern detection in Day04 solution

fix: Remove extra `end` in day4.ex module
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Ruidy (aider) 2024-12-04 13:32:59 +01:00 committed by Ruidy
parent 02502b0788
commit 20d5b2f1f3
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1 changed files with 33 additions and 16 deletions
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lib/advent_code2024/solutions/day04/day4.ex
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@ -98,7 +98,7 @@ defmodule AdventCode2024.Solutions.Day04 do
]
grid_chars = Enum.map(grid, &String.graphemes/1)
grid_chars
|> Enum.with_index()
|> Enum.reduce(0, fn {row, row_idx}, acc ->
@ -122,24 +122,41 @@ defmodule AdventCode2024.Solutions.Day04 do
end
defp find_xmas?(grid, {row, col}, {d_row, d_col}) do
# Define the positions for the X shape
positions = [
# Define the positions for the X pattern
positions_right = [
# M
{row, col},
# A
{row + d_row, col + d_col},
{row + 2 * d_row, col + 2 * d_col},
{row + d_row, col - d_col}
# S
{row + 2 * d_row, col + 2 * d_col}
]
# Check if all positions contain the correct letters for "MAS"
Enum.with_index(positions)
|> Enum.all?(fn {{r, c}, idx} ->
within_bounds?(grid, r, c) &&
case idx do
0 -> Enum.at(Enum.at(grid, r), c) == "M"
1 -> Enum.at(Enum.at(grid, r), c) == "A"
2 -> Enum.at(Enum.at(grid, r), c) == "S"
3 -> Enum.at(Enum.at(grid, r), c) == "S"
end
end)
positions_left = [
# M
{row, col + 2 * d_col},
# A (center shared)
{row + d_row, col + d_col},
# S
{row + 2 * d_row, col}
]
# Check both diagonals for "MAS" (can be forwards or backwards)
(check_mas?(grid, positions_right) or check_sam?(grid, positions_right)) and
(check_mas?(grid, positions_left) or check_sam?(grid, positions_left))
end
defp check_mas?(grid, [{r1, c1}, {r2, c2}, {r3, c3}]) do
within_bounds?(grid, r1, c1) and within_bounds?(grid, r2, c2) and within_bounds?(grid, r3, c3) and
Enum.at(Enum.at(grid, r1), c1) == "M" and
Enum.at(Enum.at(grid, r2), c2) == "A" and
Enum.at(Enum.at(grid, r3), c3) == "S"
end
defp check_sam?(grid, [{r1, c1}, {r2, c2}, {r3, c3}]) do
within_bounds?(grid, r1, c1) and within_bounds?(grid, r2, c2) and within_bounds?(grid, r3, c3) and
Enum.at(Enum.at(grid, r1), c1) == "S" and
Enum.at(Enum.at(grid, r2), c2) == "A" and
Enum.at(Enum.at(grid, r3), c3) == "M"
end
end