advent-of-code/aoc2018/src/day04.rs

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Rust
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2019-11-25 19:04:48 +01:00
use std::collections::HashMap;
use std::error::Error;
use std::str::FromStr;
use super::err;
use super::Result;
const INPUT: &str = include_str!("../input/day04.txt");
fn sorted_lines(input: &str) -> String {
let mut lines: Vec<_> = input.lines().collect();
lines.sort_unstable();
lines.join("\n")
}
pub fn run() -> Result<()> {
println!("part 1: {}", part1(&sorted_lines(INPUT))?);
Ok(())
}
#[derive(Debug)]
enum Event {
ShiftChange(u64),
FallAsleep,
WakeUp,
}
impl FromStr for Event {
type Err = Box<dyn Error>;
fn from_str(s: &str) -> Result<Self> {
if s.find("wakes up").is_some() {
Ok(Event::WakeUp)
} else if s.find("falls asleep").is_some() {
Ok(Event::FallAsleep)
} else if s.find("begins shift").is_some() {
let pound = s.find('#').ok_or_else(|| err!("`#` not found"))?;
let s = &s[(pound + 1)..];
let space = s.find(' ').ok_or_else(|| err!("` ` not found after `#`"))?;
let id = s[..space].parse()?;
Ok(Event::ShiftChange(id))
} else {
Err(err!("unknown event type"))
}
}
}
#[derive(Debug)]
struct Date {
year: u32,
month: u8,
day: u8,
hour: u8,
minute: u8,
}
impl FromStr for Date {
type Err = Box<dyn Error>;
fn from_str(s: &str) -> Result<Self> {
let lbracket = s.find('[').ok_or_else(|| err!("`[` not found"))?;
let s = &s[(lbracket + 1)..];
let dash = s.find('-').ok_or_else(|| err!("`-` not found"))?;
let year = s[..dash].parse()?;
let s = &s[(dash + 1)..];
let dash = s.find('-').ok_or_else(|| err!("`-` not found"))?;
let month = s[..dash].parse()?;
let s = &s[(dash + 1)..];
let space = s.find(' ').ok_or_else(|| err!("` ` not found"))?;
let day = s[..space].parse()?;
let s = &s[(space + 1)..];
let colon = s.find(':').ok_or_else(|| err!("`:` not found"))?;
let hour = s[..colon].parse()?;
let s = &s[(colon + 1)..];
let rbracket = s.find(']').ok_or_else(|| err!("`]` not found"))?;
let minute = s[..rbracket].parse()?;
Ok(Date {
year,
month,
day,
hour,
minute,
})
}
}
#[derive(Debug)]
struct LogEntry {
date: Date,
event: Event,
}
impl FromStr for LogEntry {
type Err = Box<dyn Error>;
fn from_str(s: &str) -> Result<Self> {
let date: Date = s.parse().map_err(|e| err!("couldn't parse date: {}", e))?;
let event = s.parse().map_err(|e| err!("couldn't parse event: {}", e))?;
let entry = LogEntry { date, event };
match entry.event {
Event::FallAsleep | Event::WakeUp => {
assert!(entry.date.hour == 0);
}
_ => {}
};
Ok(entry)
}
}
fn part1(input: &str) -> Result<u64> {
let mut guard_id = None;
let mut map: HashMap<u64, Vec<LogEntry>> = HashMap::new();
for line in input.lines() {
let log_entry: LogEntry = line.parse()?;
if let Event::ShiftChange(id) = log_entry.event {
guard_id = Some(id);
}
match guard_id {
Some(id) => map.entry(id).or_default().push(log_entry),
None => return Err(err!("event before first shift")),
}
}
// Fill frequency by minute and by guard
let mut sleep_freq_per_guard = HashMap::new();
for (id, log_entries) in map {
let mut fell_asleep = None;
let mut sleep_freq: HashMap<u8, u64> = HashMap::new();
for e in log_entries {
match e.event {
Event::ShiftChange(_) => fell_asleep = None, // new day!
Event::FallAsleep => fell_asleep = Some(e.date.minute),
Event::WakeUp => match fell_asleep {
Some(asleep) => {
let awake = e.date.minute;
for m in asleep..awake {
*sleep_freq.entry(m).or_default() += 1;
}
fell_asleep = None;
}
None => return Err(err!("woke up before falling asleep")),
},
}
}
if fell_asleep.is_some() {
return Err(err!("fell asleep but never woke up!"));
}
sleep_freq_per_guard.insert(id, sleep_freq);
}
let (heavy_sleeper, _) = sleep_freq_per_guard
.iter()
.max_by_key(|(_, freqs)| freqs.values().sum::<u64>())
.unwrap();
let heavy_sleeper_freq = &sleep_freq_per_guard[heavy_sleeper];
let (best_minute, _) = heavy_sleeper_freq
.iter()
.max_by_key(|(_, freq)| *freq)
.unwrap();
Ok((*best_minute as u64) * heavy_sleeper)
}
#[cfg(test)]
mod tests {
use super::*;
const PROVIDED: &str = "[1518-11-01 00:00] Guard #10 begins shift
[1518-11-01 00:05] falls asleep
[1518-11-01 00:25] wakes up
[1518-11-01 00:30] falls asleep
[1518-11-01 00:55] wakes up
[1518-11-01 23:58] Guard #99 begins shift
[1518-11-02 00:40] falls asleep
[1518-11-02 00:50] wakes up
[1518-11-03 00:05] Guard #10 begins shift
[1518-11-03 00:24] falls asleep
[1518-11-03 00:29] wakes up
[1518-11-04 00:02] Guard #99 begins shift
[1518-11-04 00:36] falls asleep
[1518-11-04 00:46] wakes up
[1518-11-05 00:03] Guard #99 begins shift
[1518-11-05 00:45] falls asleep
[1518-11-05 00:55] wakes up
";
#[test]
fn part1_provided() {
assert_eq!(part1(PROVIDED).unwrap(), 240);
}
#[test]
fn part1_real() {
assert_eq!(part1(&sorted_lines(INPUT)).unwrap(), 142515);
}
}