69 lines
1.4 KiB
Rust
69 lines
1.4 KiB
Rust
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use std::fmt::Write;
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use anyhow::{Context, Result};
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const INPUT: &str = include_str!("../input/day08.txt");
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pub fn run() -> Result<String> {
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let mut res = String::with_capacity(128);
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writeln!(res, "part 1: {}", part1(INPUT)?)?;
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Ok(res)
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}
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fn part1(input: &str) -> Result<usize> {
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let entries = input
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.lines()
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.map(TryInto::try_into)
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.collect::<Result<Vec<Entry>>>()?;
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Ok(entries.iter().map(Entry::count_easy_digits_in_output).sum())
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}
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struct Entry<'a> {
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four_digits_output: Vec<&'a str>,
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}
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impl<'a> Entry<'a> {
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fn count_easy_digits_in_output(&self) -> usize {
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self.four_digits_output
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.iter()
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.filter(|digit| Self::is_easy_digit(digit))
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.count()
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}
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fn is_easy_digit(digit: &str) -> bool {
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matches!(digit.len(), 2 | 3 | 4 | 7)
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}
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}
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impl<'a> TryFrom<&'a str> for Entry<'a> {
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type Error = anyhow::Error;
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fn try_from(s: &'a str) -> Result<Self, Self::Error> {
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let (_, output) = s.split_once(" | ").context("couldn't split on ` | `")?;
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Ok(Self {
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four_digits_output: output.trim().split(' ').collect(),
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})
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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const PROVIDED: &str = include_str!("../input/day08_provided.txt");
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#[test]
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fn part1_provided() {
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assert_eq!(part1(PROVIDED).unwrap(), 26);
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}
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#[test]
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fn part1_real() {
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assert_eq!(part1(INPUT).unwrap(), 488);
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}
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}
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