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185 lines
4.8 KiB
185 lines
4.8 KiB
use std::collections::HashMap;
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use std::error::Error;
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use std::io::{self, Read};
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use std::ops::Range;
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use pest::iterators::Pair;
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use pest::Parser;
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use pest_derive::Parser;
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fn main() -> Result<(), Box<Error>> {
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let mut input = String::new();
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io::stdin().read_to_string(&mut input)?;
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let output = solve(&input)?;
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println!("{}", output);
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Ok(())
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}
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fn solve(input: &str) -> Result<String, Box<Error>> {
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let records = Record::parse(input)?;
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let mut stats = HashMap::new();
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for record in records {
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let minute_stats = stats.entry(record.guard_id).or_insert_with(HashMap::new);
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let minutes: Vec<_> = record
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.sleep_ranges
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.into_iter()
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.flat_map(|x| x.collect::<Vec<_>>())
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.collect();
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for minute in minutes {
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let count = minute_stats.entry(minute).or_insert(0);
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*count += 1
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}
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}
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// Part One
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// let (guard, minute_stats) = stats
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// .iter()
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// .max_by_key::<usize, _>(|(_, v)| v.iter().map(|(_, v)| v).sum())
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// .unwrap();
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// let (minute, _) = minute_stats.iter().max_by_key(|(_, &v)| v).unwrap();
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// Part Two
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let (guard, (minute, _)) = stats
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.iter()
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.flat_map(|(k, minute_counts)| minute_counts.iter().max_by_key(|(_, &v)| v).map(|v| (k, v)))
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.max_by_key(|(_, (_, &v))| v)
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.unwrap();
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Ok((guard * minute).to_string())
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}
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#[test]
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fn test_solve() {
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let input = r"
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[1518-11-01 00:00] Guard #10 begins shift
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[1518-11-01 00:05] falls asleep
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[1518-11-01 00:25] wakes up
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[1518-11-01 00:30] falls asleep
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[1518-11-01 00:55] wakes up
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[1518-11-01 23:58] Guard #99 begins shift
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[1518-11-02 00:40] falls asleep
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[1518-11-02 00:50] wakes up
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[1518-11-03 00:05] Guard #10 begins shift
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[1518-11-03 00:24] falls asleep
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[1518-11-03 00:29] wakes up
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[1518-11-04 00:02] Guard #99 begins shift
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[1518-11-04 00:36] falls asleep
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[1518-11-04 00:46] wakes up
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[1518-11-05 00:03] Guard #99 begins shift
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[1518-11-05 00:45] falls asleep
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[1518-11-05 00:55] wakes up
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"
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.trim();
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let output = solve(input).unwrap();
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// Part One
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// assert_eq!(output, "240".to_string());
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// Part Two
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assert_eq!(output, "4455".to_string());
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}
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#[derive(Debug)]
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struct Record {
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guard_id: usize,
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sleep_ranges: Vec<Range<usize>>,
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}
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impl Record {
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fn parse(s: &str) -> Result<Vec<Record>, Box<Error>> {
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let mut records: Vec<_> = s.lines().collect();
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records.sort();
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let input = records.join("\n");
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let mut parsed = RecordsParser::parse(Rule::records, &input)?;
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let records: Vec<Record> = parsed
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.next()
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.unwrap()
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.into_inner()
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.flat_map(|record| match record.as_rule() {
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Rule::record => Some(record.into()),
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Rule::EOI => None,
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_ => unreachable!(),
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})
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.collect();
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Ok(records)
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}
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fn parse_sleep_range(pair: Pair<Rule>) -> Range<usize> {
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let mut sleep_range = pair.into_inner();
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let falls_asleep: usize = Self::parse_minute(sleep_range.next().unwrap());
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let wakes_up: usize = Self::parse_minute(sleep_range.next().unwrap());
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(falls_asleep..wakes_up)
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}
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fn parse_minute(pair: Pair<Rule>) -> usize {
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pair.into_inner().next().unwrap().as_str().parse().unwrap()
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}
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}
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#[test]
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fn test_parsing() {
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let input = r"
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[1518-11-01 00:00] Guard #10 begins shift
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[1518-11-01 00:05] falls asleep
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[1518-11-01 00:25] wakes up
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[1518-11-01 00:30] falls asleep
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[1518-11-01 00:55] wakes up
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[1518-11-01 23:58] Guard #99 begins shift
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[1518-11-02 00:40] falls asleep
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[1518-11-02 00:50] wakes up
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[1518-11-03 00:05] Guard #10 begins shift
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[1518-11-03 00:24] falls asleep
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[1518-11-03 00:29] wakes up
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[1518-11-04 00:02] Guard #99 begins shift
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[1518-11-04 00:36] falls asleep
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[1518-11-04 00:46] wakes up
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[1518-11-05 00:03] Guard #99 begins shift
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[1518-11-05 00:45] falls asleep
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[1518-11-05 00:55] wakes up
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"
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.trim();
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let records = Record::parse(input).unwrap();
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assert_eq!(records.len(), 5);
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let record = &records[0];
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assert_eq!(record.guard_id, 10);
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assert_eq!(record.sleep_ranges, vec![(5..25), (30..55)]);
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}
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impl<'a> From<Pair<'a, Rule>> for Record {
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fn from(pair: Pair<Rule>) -> Self {
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let mut record = pair.into_inner();
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let guard_id = record
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.next()
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.unwrap()
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.into_inner()
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.nth(1) // skip the minute
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.unwrap()
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.as_str()
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.parse()
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.unwrap();
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let sleep_ranges: Vec<_> = record
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.next()
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.unwrap()
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.into_inner()
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.map(Self::parse_sleep_range)
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.collect();
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Record {
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guard_id,
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sleep_ranges,
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}
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}
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}
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#[derive(Parser)]
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#[grammar = "day_04.pest"]
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#[allow(dead_code)]
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struct RecordsParser;
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