Catching up after the weekend. Not the best, but will do.
defmodule Aoc2025.Solutions.Y25.Day06 do
alias AoC.Input
def parse(input, _part) do
Input.read!(input)
|> String.split("\n", trim: true)
end
def part_one(problem) do
problem
|> Enum.flat_map(&(String.split(&1) |> Enum.with_index()))
|> Enum.reverse()
|> Enum.group_by(fn {x, y} -> y end, fn {x, y} -> x end)
|> Map.values()
|> Enum.map(fn [op | numbers] -> build_expr_and_calc(numbers, op) end)
|> Enum.sum()
end
def part_two(rows) do
col_sizes =
rows
|> Enum.map(&fetch_space_locations/1)
|> Enum.zip_reduce([], &fetch_max_col_size/2)
|> Enum.reverse()
Enum.map(rows, fn row -> split_row(row, col_sizes) end)
|> Enum.zip_with(&(&1 |> Enum.reverse()))
|> Enum.map(fn [op | col] -> [op | Enum.zip_with(Enum.reverse(col), & &1)] end)
|> Enum.map(fn [op | numbers] -> build_expr_and_calc(numbers, op) end)
|> Enum.sum()
end
def build_expr_and_calc(numbers, op) do
numbers |> Enum.intersperse(op) |> List.to_string() |> Code.eval_string() |> elem(0)
end
def fetch_space_locations(rows) do
Regex.scan(~r/[\d\*\+]+/, rows, return: :index, trim: true) |> List.flatten()
end
def fetch_max_col_size(els, acc) do
[Enum.max_by(els, fn {x, y} -> y end) | acc]
end
def split_row(row, col_sizes) do
Enum.map(col_sizes, fn {start, size} ->
String.slice(row, start, size) |> String.to_charlist()
end)
end
end