79 lines
2 KiB
Rust
79 lines
2 KiB
Rust
#![warn(clippy::pedantic)]
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use nom::Parser;
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use std::io::{stdin, Read};
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use nom::{
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branch::alt, bytes::complete::tag, character::complete::u32, multi::separated_list0,
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sequence::delimited, IResult,
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};
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#[derive(Debug, Clone, PartialEq, Eq)]
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enum Data {
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List(Vec<Data>),
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Number(usize),
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}
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impl PartialOrd for Data {
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fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
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Some(self.cmp(other))
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}
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}
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impl Ord for Data {
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fn cmp(&self, other: &Self) -> std::cmp::Ordering {
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match (self, other) {
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(Data::List(l), Data::List(r)) => l.as_slice().cmp(r),
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(Data::List(l), r @ Data::Number(_)) => l.iter().cmp([r]),
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(l @ Data::Number(_), Data::List(r)) => [l].into_iter().cmp(r.iter()),
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(Data::Number(l), Data::Number(r)) => l.cmp(r),
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}
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}
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}
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fn parse_data(s: &str) -> IResult<&str, Data, ()> {
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alt((
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delimited(tag("["), separated_list0(tag(","), parse_data), tag("]")).map(Data::List),
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u32.map(|i| Data::Number(usize::try_from(i).unwrap())),
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))(s)
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}
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fn main() {
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let mut data = String::new();
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stdin().read_to_string(&mut data).unwrap();
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let pairs: Vec<_> = data
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.split("\n\n")
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.map(|pair| {
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let (left, right) = pair.split_once('\n').unwrap();
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(parse_data(left).unwrap().1, parse_data(right).unwrap().1)
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})
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.collect();
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let num_sorted: usize = pairs
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.iter()
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.enumerate()
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.filter_map(|(i, (left, right))| (left <= right).then_some(i + 1))
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.sum();
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println!("{}", num_sorted);
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let dividers = [2, 6]
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.into_iter()
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.map(|i| Data::List(vec![Data::List(vec![Data::Number(i)])]));
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let mut sorted: Vec<_> = pairs
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.into_iter()
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.flat_map(|(left, right)| [left, right])
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.collect();
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sorted.extend(dividers.clone());
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sorted.sort();
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println!(
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"{}",
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dividers
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.map(|div| sorted.binary_search(&div).unwrap() + 1)
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.product::<usize>()
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);
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}
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