2021: day06: part 1 & 2
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1
aoc2021/input/day06.txt
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1
aoc2021/input/day06.txt
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4,1,4,1,3,3,1,4,3,3,2,1,1,3,5,1,3,5,2,5,1,5,5,1,3,2,5,3,1,3,4,2,3,2,3,3,2,1,5,4,1,1,1,2,1,4,4,4,2,1,2,1,5,1,5,1,2,1,4,4,5,3,3,4,1,4,4,2,1,4,4,3,5,2,5,4,1,5,1,1,1,4,5,3,4,3,4,2,2,2,2,4,5,3,5,2,4,2,3,4,1,4,4,1,4,5,3,4,2,2,2,4,3,3,3,3,4,2,1,2,5,5,3,2,3,5,5,5,4,4,5,5,4,3,4,1,5,1,3,4,4,1,3,1,3,1,1,2,4,5,3,1,2,4,3,3,5,4,4,5,4,1,3,1,1,4,4,4,4,3,4,3,1,4,5,1,2,4,3,5,1,1,2,1,1,5,4,2,1,5,4,5,2,4,4,1,5,2,2,5,3,3,2,3,1,5,5,5,4,3,1,1,5,1,4,5,2,1,3,1,2,4,4,1,1,2,5,3,1,5,2,4,5,1,2,3,1,2,2,1,2,2,1,4,1,3,4,2,1,1,5,4,1,5,4,4,3,1,3,3,1,1,3,3,4,2,3,4,2,3,1,4,1,5,3,1,1,5,3,2,3,5,1,3,1,1,3,5,1,5,1,1,3,1,1,1,1,3,3,1
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126
aoc2021/src/day06.rs
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126
aoc2021/src/day06.rs
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use std::fmt::Write;
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use std::str;
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use anyhow::Result;
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const INPUT: &str = include_str!("../input/day06.txt");
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const SPAWNING_DELAY: u8 = 7;
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const TURNS_PART_1: usize = 80;
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const TURNS_PART_2: usize = 256;
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pub fn run() -> Result<String> {
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let mut res = String::with_capacity(128);
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writeln!(res, "part 1: {}", part1(INPUT)?)?;
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writeln!(res, "part 2: {}", part2(INPUT)?)?;
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Ok(res)
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}
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fn part1(input: &str) -> Result<usize> {
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let mut school = input
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.trim()
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.split(',')
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.map(str::parse::<LanternFish>)
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.collect::<Result<Vec<_>>>()?;
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for _ in 0..TURNS_PART_1 {
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let mut newly_spawned = 0;
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for fish in &mut school {
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if fish.next_turn() {
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newly_spawned += 1;
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}
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}
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school.resize_with(school.len() + newly_spawned, LanternFish::default)
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}
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Ok(school.len())
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}
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fn part2(input: &str) -> Result<usize> {
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let mut school = input.trim().parse::<School>()?;
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for _ in 0..TURNS_PART_2 {
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school.next_turn();
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}
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Ok(school.size())
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}
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struct LanternFish {
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timer: u8,
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}
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impl LanternFish {
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fn spawn() -> Self {
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LanternFish {
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timer: SPAWNING_DELAY + 1,
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}
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}
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fn next_turn(&mut self) -> bool {
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if self.timer == 0 {
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self.timer = SPAWNING_DELAY - 1;
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true
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} else {
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self.timer -= 1;
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false
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}
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}
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}
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impl Default for LanternFish {
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fn default() -> Self {
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Self::spawn()
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}
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}
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struct School {
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fish_timers: [usize; SPAWNING_DELAY as usize + 2],
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}
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impl School {
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fn next_turn(&mut self) {
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let newly_spawned = self.fish_timers[0];
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for i in 1..self.fish_timers.len() {
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self.fish_timers[i - 1] = self.fish_timers[i];
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}
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self.fish_timers[SPAWNING_DELAY as usize - 1] += newly_spawned;
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*self.fish_timers.last_mut().unwrap() = newly_spawned;
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}
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fn size(&self) -> usize {
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self.fish_timers.iter().sum()
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}
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}
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impl std::str::FromStr for School {
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type Err = anyhow::Error;
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fn from_str(s: &str) -> Result<Self> {
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let mut fish_timers = [0usize; SPAWNING_DELAY as usize + 2];
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for fish in s.split(',').map(str::parse::<usize>) {
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let fish = fish?;
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fish_timers[fish] += 1;
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}
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Ok(School { fish_timers })
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}
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}
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impl std::str::FromStr for LanternFish {
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type Err = anyhow::Error;
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fn from_str(s: &str) -> Result<Self> {
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Ok(LanternFish { timer: s.parse()? })
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}
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}
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#[cfg(test)]
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mod tests {}
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@ -5,3 +5,4 @@ pub mod day02;
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pub mod day03;
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pub mod day04;
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pub mod day05;
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pub mod day06;
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@ -7,9 +7,17 @@ use aoc2021::day02;
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use aoc2021::day03;
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use aoc2021::day04;
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use aoc2021::day05;
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use aoc2021::day06;
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fn main() -> Result<()> {
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let days: &[DayFunc] = &[day01::run, day02::run, day03::run, day04::run, day05::run];
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let days: &[DayFunc] = &[
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day01::run,
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day02::run,
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day03::run,
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day04::run,
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day05::run,
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day06::run,
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];
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aoc::run(days)
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}
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