Day 13, puzzle 1
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14
src/bin/d13p1.rs
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14
src/bin/d13p1.rs
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use aoc22::{day13, util};
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pub fn main() {
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let pairs = day13::parse_pairs(&util::parse_input());
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let mut sum = 0;
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for (i, pair) in pairs.iter().enumerate() {
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if pair.0 < pair.1 {
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sum += i + 1;
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}
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}
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println!("Sum of indices of pairs in right order: {}", sum);
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}
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116
src/day13.rs
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116
src/day13.rs
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use std::cmp::Ordering;
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use itertools::{EitherOrBoth, Itertools};
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#[derive(Debug)]
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pub enum Node {
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List(Vec<Node>),
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Num(usize),
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}
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impl PartialOrd for Node {
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fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
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match self {
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Node::List(l1) => match other {
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Node::Num(n2) => self.partial_cmp(&Node::List(vec![Node::Num(*n2)])),
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Node::List(l2) => {
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for pair in l1.iter().zip_longest(l2.iter()) {
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match pair {
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EitherOrBoth::Both(n1, n2) => {
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if n1 < n2 {
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return Some(Ordering::Less);
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} else if n2 < n1 {
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return Some(Ordering::Greater);
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}
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}
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EitherOrBoth::Left(_) => return Some(Ordering::Greater),
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EitherOrBoth::Right(_) => return Some(Ordering::Less),
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}
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}
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Some(Ordering::Equal)
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}
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},
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Node::Num(n1) => match other {
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Node::Num(n2) => n1.partial_cmp(n2),
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Node::List(_) => Node::List(vec![Node::Num(*n1)]).partial_cmp(other),
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},
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}
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}
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}
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impl PartialEq for Node {
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fn eq(&self, other: &Self) -> bool {
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self.partial_cmp(other) == Some(Ordering::Equal)
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}
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fn ne(&self, other: &Self) -> bool {
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!self.eq(other)
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}
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}
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pub fn parse_pairs(input: &String) -> Vec<(Node, Node)> {
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let mut result = Vec::new();
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for mut p in &input.lines().chunks(3) {
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let first = parse_list(p.next().unwrap()).0;
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let second = parse_list(p.next().unwrap()).0;
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assert!(p.next().unwrap_or("").is_empty());
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result.push((first, second));
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}
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result
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}
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enum ParseState {
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Idle,
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InNumber,
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}
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fn parse_list(line: &str) -> (Node, usize) {
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assert_eq!(line.chars().next(), Some('['));
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let mut state = ParseState::Idle;
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let mut i = 1;
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let mut result = Vec::new();
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let mut num_start = 0;
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while i < line.len() {
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let c = line.chars().nth(i).unwrap();
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match state {
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ParseState::Idle => {
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if c == '[' {
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let (n, inc) = parse_list(&line[i..]);
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result.push(n);
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i += inc;
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} else if c == ']' {
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// End of list reached
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break;
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} else if c.is_numeric() {
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num_start = i;
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state = ParseState::InNumber;
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} else if c != ',' {
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panic!("Unknown char: {}", c);
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}
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}
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ParseState::InNumber => {
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if c == ',' {
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let slice = &line[num_start..i];
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result.push(Node::Num(slice.parse().unwrap()));
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state = ParseState::Idle;
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} else if c == ']' {
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// End of list reached
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let slice = &line[num_start..i];
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result.push(Node::Num(slice.parse().unwrap()));
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break;
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} else if !c.is_numeric() {
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panic!("Unknown digit {}", c);
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}
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}
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}
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i += 1;
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}
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(Node::List(result), i)
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}
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@ -2,6 +2,7 @@ pub mod day1;
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pub mod day10;
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pub mod day11;
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pub mod day12;
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pub mod day13;
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pub mod day2;
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pub mod day3;
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pub mod day4;
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