72 lines
1.9 KiB
Rust
72 lines
1.9 KiB
Rust
//! Day 02 of 2020.
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use crate::prelude::*;
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/// Get the solution for day 02 of 2020.
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pub fn solution() -> Solution {
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Solution::new(Day::new(2, 2020), part_1, part_2).with_expected(638, 699)
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}
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/// The data for each line of the puzzle input.
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#[derive(Debug)]
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struct Item {
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/// The minimum amount of times the letter has to be in the password.
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min: usize,
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/// The maximum amount of times the letter has to be in the password.
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max: usize,
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/// The letter that must be in the password.
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letter: String,
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/// The password to check.
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password: String,
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}
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/// Parse all the [`Item`]s inside the puzzle input.
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fn parse_items(input: &str) -> Vec<Item> {
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let mut items = vec![];
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for line in input.lines() {
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// TODO: Replace with regex.
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let min = &line[0..line.find('-').unwrap()];
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let max = &line[line.find('-').unwrap() + 1..line.find(' ').unwrap()];
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let letter = &line[line.find(' ').unwrap() + 1..line.find(':').unwrap()];
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let password = &line[line.find(": ").unwrap() + 2..];
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items.push(Item {
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min: min.parse().unwrap(),
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max: max.parse().unwrap(),
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letter: letter.to_string(),
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password: password.to_string(),
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})
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}
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items
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}
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/// The logic to solve part one.
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fn part_1(input: &str) -> Result<String> {
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Ok(
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parse_items(input)
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.into_iter()
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.filter(|item| item.password.matches(&item.letter).count() >= item.min)
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.filter(|item| item.password.matches(&item.letter).count() <= item.max)
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.count()
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.to_string(),
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)
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}
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/// The logic to solve part two.
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fn part_2(input: &str) -> Result<String> {
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Ok(
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parse_items(input)
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.into_iter()
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.filter(|item| {
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let letter = item.letter.chars().next();
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let target_one = item.password.chars().nth(item.min - 1);
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let target_two = item.password.chars().nth(item.max - 1);
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target_one != target_two
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&& (target_one == letter || target_two == letter)
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})
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.count()
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.to_string(),
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)
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}
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