98 lines
2 KiB
Rust
98 lines
2 KiB
Rust
use std::collections::HashSet;
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use super::Result;
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const INPUT: &str = include_str!("../input/day05.txt");
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pub fn run() -> Result<()> {
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println!("part 1: {}", part1(INPUT));
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println!("part 2: {}", part2(INPUT));
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Ok(())
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}
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fn same_type(a: char, b: char) -> bool {
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a.to_ascii_lowercase() == b.to_ascii_lowercase()
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}
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fn remove_type(input: &str, c: char) -> String {
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input.chars().filter(|ch| !same_type(c, *ch)).collect()
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}
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fn collapse(input: &str) -> String {
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let mut res = String::with_capacity(input.len());
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// tracks last character of string
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let mut last: Option<char> = None;
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for next in input.chars() {
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match last {
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Some(elem) => {
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// if same type but different polarity
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if same_type(elem, next) && elem != next {
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// drop both elem and next
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last = res.pop();
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} else {
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// consider elem "safe" to push
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res.push(elem);
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last = Some(next);
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}
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}
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None => {
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last = Some(next);
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}
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}
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}
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// add last character to string if exists
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if let Some(c) = last {
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res.push(c);
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}
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res
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}
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fn part1(input: &str) -> usize {
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let res = collapse(input);
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res.len()
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}
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fn part2(input: &str) -> usize {
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let mut set = HashSet::new();
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for c in input.chars() {
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set.insert(c.to_ascii_lowercase());
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}
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set.iter()
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.map(|c| collapse(&remove_type(input, *c)).len())
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.min()
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.unwrap()
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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 = "dabAcCaCBAcCcaDA";
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#[test]
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fn part1_provided() {
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assert_eq!(part1(PROVIDED), 10);
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}
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#[test]
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fn part1_real() {
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assert_eq!(part1(INPUT), 10638);
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}
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#[test]
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fn part2_provided() {
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assert_eq!(part2(PROVIDED), 4);
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}
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#[test]
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fn part2_real() {
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assert_eq!(part2(INPUT), 4944);
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}
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}
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