73 lines
1.8 KiB
Rust
73 lines
1.8 KiB
Rust
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use color_eyre::{eyre::eyre, Result};
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mod display;
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use display::{CharSet, Display};
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pub fn solve() -> Result<()> {
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let input_data = include_str!("../../data/day_08.txt").trim();
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println!("Day 08 Part 1: {}", part_1(input_data)?);
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println!("Day 08 Part 2: {}", part_2(input_data)?);
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Ok(())
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}
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fn part_1(input: &str) -> Result<usize> {
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Ok(
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input
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.lines()
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.map(|line| {
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line
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.split(" | ")
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.nth(1)
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.ok_or(eyre!("Invalid input: {}", line))
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})
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.collect::<Result<Vec<_>>>()?
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.into_iter()
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.flat_map(|line| line.split(" ").map(Display::parse))
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.filter(|display| [2, 4, 3, 7].contains(&display.0))
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.count(),
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)
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}
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fn part_2(input: &str) -> Result<isize> {
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let mut sum = 0;
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for line in input.lines() {
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let mut split = line.split(" | ");
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// Figure out the displays from the signal side.
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let displays = Display::figure_out_from_others(
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split
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.next()
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.ok_or(eyre!("Invalid input: {}", line))?
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.split(" ")
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.map(Display::parse)
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.collect::<Vec<_>>(),
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)?;
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// Get all the CharSets from the encoded side.
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let encoded = split
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.next()
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.ok_or(eyre!("Invalid input: {}", line))?
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.split(" ")
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.map(str::chars)
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.map(CharSet::from_iter)
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.collect::<Vec<_>>();
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// Loop through the encoded numbers backwards so we can use the loop index
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// to multiply it by 10 to the power of the index.
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// So 123 would be (3 * 1) + (2 * 10) + (1 * 100).
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for (index, set) in encoded.into_iter().rev().enumerate() {
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let decoded_number = displays
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.iter()
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.find(|display| display.1 == &set)
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.map(|display| display.0)
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.ok_or(eyre!("Impossible to decode {:?}", set))?;
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sum += 10_isize.pow(index as u32) * decoded_number;
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}
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}
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Ok(sum)
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}
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