mirror of
https://github.com/rjNemo/ai_advent_code_2024
synced 2026-06-06 02:26:44 +00:00
101 lines
2.5 KiB
Elixir
101 lines
2.5 KiB
Elixir
defmodule AdventCode2024.Solutions.Day04 do
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@behaviour AdventCode2024.Solution
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@default_input "priv/inputs/day04/input.txt"
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def count_word_occurrences(grid, word) do
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grid
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|> Enum.map(&String.graphemes/1)
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|> find_word(word)
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end
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defp find_word(grid, word) do
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directions = [
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# Right
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{0, 1},
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# Down
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{1, 0},
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# Left
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{0, -1},
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# Up
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{-1, 0},
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# Down-right diagonal
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{1, 1},
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# Up-left diagonal
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{-1, -1},
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# Down-left diagonal
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{1, -1},
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# Up-right diagonal
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{-1, 1}
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]
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grid
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|> Enum.with_index()
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|> Enum.reduce(0, fn {row, row_idx}, acc ->
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row
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|> Enum.with_index()
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|> Enum.reduce(acc, fn {_, col_idx}, acc_inner ->
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acc_inner + count_word_from(grid, word, {row_idx, col_idx}, directions)
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end)
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end)
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end
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@doc """
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Counts the occurrences of a word in all possible directions from a given starting position in the grid.
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## Parameters
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- grid: A 2D list representing the word search grid.
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- word: The word to be searched for.
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- row: The starting row index.
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- col: The starting column index.
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- directions: A list of tuples representing the directions to search in.
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## Returns
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- The number of times the word is found from the given starting position in the grid.
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"""
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defp count_word_from(grid, word, {row, col}, directions) do
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directions
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|> Enum.reduce(0, fn direction, acc ->
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if find_word?(grid, word, {row, col}, direction) do
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acc + 1
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else
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acc
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end
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end)
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end
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defp find_word?(grid, word, {row, col}, {d_row, d_col}) do
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word
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|> String.codepoints()
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|> Enum.with_index()
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|> Enum.all?(fn {char, i} ->
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new_row = row + i * d_row
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new_col = col + i * d_col
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within_bounds?(grid, new_row, new_col) && Enum.at(Enum.at(grid, new_row), new_col) == char
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end)
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end
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defp within_bounds?(grid, row, col) do
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row >= 0 && row < length(grid) && col >= 0 && col < length(Enum.at(grid, 0))
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end
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@doc """
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Reads a grid from a file and counts the occurrences of a word using `count_word/2`.
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## Parameters
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- file_path: The path to the file containing the grid.
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- word: The word to be searched for.
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## Returns
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- The number of times the word is found in the grid.
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"""
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def solve(file_path \\ @default_input) do
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file_path
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|> File.stream!()
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|> Enum.map(&String.trim/1)
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|> count_word_occurrences("XMAS")
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end
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def solve_part2(_input_file) do
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end
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end
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