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day8
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| defmodule Day8 do | |
| defmodule Node do | |
| defstruct children_count: 0, metadata_count: 0, metadata: [], children: [] | |
| def parse_header(numbers) do | |
| {[children_count, metadata_count], numbers} = Enum.split(numbers, 2) | |
| node = %Node{children_count: children_count, metadata_count: metadata_count} | |
| {node, numbers} | |
| end | |
| def parse_children({%Node{children_count: 0} = node, numbers}) do | |
| {node, numbers} | |
| end | |
| def parse_children({node, numbers}) do | |
| {numbers, children} = | |
| Enum.reduce((1..node.children_count), {numbers, []}, fn _x, {numbers, children} -> | |
| {child, numbers} = Node.tree(numbers) | |
| {numbers, children ++ [child]} | |
| end) | |
| {%Node{node | children: children}, numbers} | |
| end | |
| def parse_metadata({%Node{metadata_count: metadata_count} = node, numbers}) do | |
| {metadata, numbers} = Enum.split(numbers, metadata_count) | |
| {%Node{node | metadata: metadata}, numbers} | |
| end | |
| def tree(numbers) do | |
| numbers | |
| |> parse_header | |
| |> parse_children | |
| |> parse_metadata | |
| end | |
| def sum_metadata(%Node{children: children, metadata: metadata}) do | |
| Enum.reduce(children, Enum.sum(metadata), fn node, sum -> | |
| sum + Node.sum_metadata(node) | |
| end) | |
| end | |
| def value(%Node{children: [], metadata: metadata}) do | |
| Enum.sum(metadata) | |
| end | |
| def value(nil) do | |
| 0 | |
| end | |
| def value(%Node{children: children, metadata: metadata}) do | |
| Enum.reduce(metadata, 0, fn i, sum -> | |
| sum + Node.value(Enum.at(children, i - 1)) | |
| end) | |
| end | |
| end | |
| @doc """ | |
| Parses line to list of integers | |
| iex> Day8.parse("2 3 0 3 10 11 12 1 1 0 1 99 2 1 1 2") | |
| [2, 3, 0, 3, 10, 11, 12, 1, 1, 0, 1, 99, 2, 1, 1, 2] | |
| """ | |
| def numbers(line) do | |
| line | |
| |> String.split | |
| |> Enum.map(&String.to_integer/1) | |
| end | |
| def part1 do | |
| {node, _} = | |
| File.read!("input.txt") | |
| |> numbers() | |
| |> Node.tree() | |
| Node.sum_metadata(node) | |
| end | |
| def part2 do | |
| {node, _} = | |
| File.read!("input.txt") | |
| |> numbers() | |
| |> Node.tree() | |
| Node.value(node) | |
| end | |
| end |
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