advent-of-code/2021/src/bin/day10.rs
2021-12-10 22:51:24 +01:00

104 lines
2.6 KiB
Rust

#![feature(test)]
extern crate test;
use aoc2021::common::*;
const DAY: usize = 10;
fn solve(input: &str) -> (usize, usize) {
let mut p1_score = 0;
let mut p2_scores = Vec::new();
let mut stack = Vec::new();
for line in input.lines() {
match is_well_formed(line, &mut stack) {
Ok(s) => p2_scores.push(autocomplete_points(s)), // <- clears the stack internally
Err(p) => {
p1_score += p;
stack.clear();
}
}
}
let p2_len = p2_scores.len();
(p1_score, *p2_scores.select_nth_unstable(p2_len / 2).1)
}
fn is_well_formed<'a>(line: &str, stack: &'a mut Vec<u8>) -> Result<&'a mut Vec<u8>, usize> {
for c in line.bytes() {
match c {
b'(' | b'[' | b'<' | b'{' => stack.push(c),
b']' | b'}' | b'>' if stack.last().unwrap() + 2 == c => {
stack.pop();
}
b')' if stack.last().unwrap() == &b'(' => {
stack.pop();
}
b')' => return Err(3),
b']' => return Err(57),
b'}' => return Err(1197),
b'>' => return Err(25137),
_ => unreachable!(),
}
}
Ok(stack)
}
fn autocomplete_points(stack: &mut Vec<u8>) -> usize {
let mut points = 0;
for p in stack.drain(..).rev() {
points *= 5;
match p {
b'(' => points += 1,
b'[' => points += 2,
b'{' => points += 3,
b'<' => points += 4,
_ => unreachable!(),
}
}
points
}
fn main() {
let raw = read_file(DAY);
let (p1, p2) = solve(&raw);
println!("Part 1: {p1}");
println!("Part 2: {p2}");
}
#[cfg(test)]
mod tests {
use super::*;
use aoc2021::*;
const TEST_INPUT: &str = "[({(<(())[]>[[{[]{<()<>>
[(()[<>])]({[<{<<[]>>(
{([(<{}[<>[]}>{[]{[(<()>
(((({<>}<{<{<>}{[]{[]{}
[[<[([]))<([[{}[[()]]]
[{[{({}]{}}([{[{{{}}([]
{<[[]]>}<{[{[{[]{()[[[]
[<(<(<(<{}))><([]([]()
<{([([[(<>()){}]>(<<{{
<{([{{}}[<[[[<>{}]]]>[]]";
#[bench]
fn bench_autocomplete_points(b: &mut test::Bencher) {
let sample_stack = vec![b'<', b'{', b'(', b'['];
b.iter(|| assert_eq!(autocomplete_points(test::black_box(&mut sample_stack.clone())), 294));
}
#[test]
fn part1_test() {
assert_eq!(solve(TEST_INPUT).0, 26397);
}
#[test]
fn part2_test() {
assert_eq!(solve(TEST_INPUT).1, 288957);
}
#[bench]
fn bench_solution(b: &mut test::Bencher) {
let raw = read_file(DAY);
b.iter(|| assert_eq!(solve(test::black_box(&raw)), (358737, 4329504793)))
}
}