mirror of
https://github.com/rjNemo/ai_advent_code_2024
synced 2026-06-06 02:26:44 +00:00
107 lines
3.1 KiB
Elixir
107 lines
3.1 KiB
Elixir
defmodule AdventCode2024.Day1 do
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@behaviour AdventCode2024.Solution
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@moduledoc """
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Solution for Advent of Code 2024 - Day 1: Historian Hysteria
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This module processes pairs of numbers from an input file to:
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- Calculate total distance between paired numbers (Part 1)
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- Calculate similarity scores based on frequency matching (Part 2)
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Input file format expects lines with two space-separated integers.
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"""
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@type result :: {:ok, integer()} | {:error, String.t()}
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@type number_pair :: {[integer()], [integer()]}
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@doc """
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Solves Part 1 of Day 1 challenge.
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Takes an input file path and calculates the total distance between paired numbers.
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## Parameters
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- input_file: Path to input file (defaults to "day1/input.txt")
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## Returns
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- `{:ok, result}` where result is the calculated total distance
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- `{:error, reason}` if file reading fails
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"""
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@spec solve(String.t()) :: result()
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def solve(input_file \\ "day1/input.txt") do
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case File.read(input_file) do
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{:ok, content} ->
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{left, right} = parse_input(content)
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result = calculate_total_distance(left, right)
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{:ok, result}
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{:error, reason} ->
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{:error, reason}
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end
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end
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defp valid_line?(line) do
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case String.split(line, ~r/\s+/, trim: true) do
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[left, right] -> match?({:ok, _}, Integer.parse(left)) && match?({:ok, _}, Integer.parse(right))
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_ -> false
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end
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end
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@doc """
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Solves Part 2 of Day 1 challenge.
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Takes an input file path and calculates similarity scores based on number frequencies.
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## Parameters
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- input_file: Path to input file (defaults to "day1/input.txt")
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## Returns
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- `{:ok, result}` where result is the similarity score
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- `{:error, reason}` if file reading fails
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"""
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@spec solve_part2(String.t()) :: result()
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def solve_part2(input_file \\ "day1/input.txt") do
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case File.read(input_file) do
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{:ok, content} ->
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{left, right} = parse_input(content)
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result = calculate_similarity_score(left, right)
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{:ok, result}
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{:error, reason} ->
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{:error, reason}
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end
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end
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@spec parse_input(String.t()) :: number_pair() | {:error, String.t()}
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defp parse_input(content) do
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lines = String.split(content, "\n", trim: true)
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if Enum.all?(lines, &valid_line?/1) do
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{left, right} =
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lines
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|> Enum.map(&String.split(&1, ~r/\s+/, trim: true))
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|> Enum.map(fn [left, right] ->
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{String.to_integer(left), String.to_integer(right)}
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end)
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|> Enum.unzip()
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{left, right}
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else
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{:error, "Invalid input format"}
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end
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end
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@spec calculate_total_distance([integer()], [integer()]) :: integer()
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defp calculate_total_distance(left, right) do
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Enum.zip(Enum.sort(left), Enum.sort(right))
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|> Enum.map(fn {a, b} -> abs(a - b) end)
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|> Enum.sum()
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end
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@spec calculate_similarity_score([integer()], [integer()]) :: integer()
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defp calculate_similarity_score(left, right) do
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frequencies = Enum.frequencies(right)
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left
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|> Enum.map(&(&1 * Map.get(frequencies, &1, 0)))
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|> Enum.sum()
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end
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end
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