99 lines
2.0 KiB
Rust
99 lines
2.0 KiB
Rust
use std::{
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collections::{HashMap, HashSet},
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fs::read_to_string,
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};
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pub fn day_main() {
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let input = read_to_string("input/day19.txt").unwrap();
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let input = input.trim();
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println!(" part1: {}", part1(input));
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println!(" part2: {}", part2(input));
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}
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type RiddleResult = usize;
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fn part1(input: &str) -> RiddleResult {
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let (a, b) = input.split_once("\n\n").unwrap();
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let towels: HashSet<&str> = a.split(", ").collect();
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b.lines().filter(|line| possible(line, &towels)).count()
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}
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fn possible(line: &str, towels: &HashSet<&str>) -> bool {
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if line.is_empty() {
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return true;
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}
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for t in towels.iter() {
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if let Some(suffix) = line.strip_prefix(t) {
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if possible(suffix, towels) {
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return true;
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}
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}
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}
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false
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}
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fn countp<'a>(
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line: &'a str,
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towels: &HashSet<&str>,
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solved: &mut HashMap<&'a str, usize>,
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) -> usize {
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if line.is_empty() {
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return 1;
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}
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if let Some(count) = solved.get(line) {
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return *count;
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}
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let mut summed = 0;
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for t in towels.iter() {
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if let Some(suffix) = line.strip_prefix(t) {
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summed += countp(suffix, towels, solved);
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}
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}
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solved.insert(line, summed);
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summed
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}
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fn part2(input: &str) -> RiddleResult {
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let (a, b) = input.split_once("\n\n").unwrap();
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let towels: HashSet<&str> = a.split(", ").collect();
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b.lines()
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.map(|line| countp(line, &towels, &mut HashMap::new()))
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.sum()
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}
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#[cfg(test)]
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mod test {
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use std::collections::HashSet;
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use crate::day19::possible;
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use super::{part1, part2};
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const TEST_INPUT: &str = r"r, wr, b, g, bwu, rb, gb, br
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brwrr
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bggr
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gbbr
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rrbgbr
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ubwu
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bwurrg
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brgr
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bbrgwb
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";
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#[test]
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fn test1() {
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assert_eq!(part1(TEST_INPUT), 6);
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}
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#[test]
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fn solver() {
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let set = HashSet::from_iter(["r", "wr", "b", "g", "bwu", "rb", "gb", "br"]);
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assert!(possible("bwurrg", &set));
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}
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#[test]
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fn test2() {
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assert_eq!(part2(TEST_INPUT), 16);
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}
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}
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