2021: day06: refacto
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@ -5,7 +5,7 @@ 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 SPAWNING_DELAY: usize = 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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@ -19,63 +19,15 @@ pub fn run() -> Result<String> {
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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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let mut school = input.trim().parse::<School>()?;
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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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Ok(school.grow_for(TURNS_PART_1))
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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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Ok(school.grow_for(TURNS_PART_2))
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}
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struct School {
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@ -90,38 +42,37 @@ impl School {
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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[SPAWNING_DELAY - 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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fn grow_for(&mut self, turns: usize) -> usize {
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for _ in 0..turns {
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self.next_turn();
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}
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self.size()
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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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let mut fish_timers = [0usize; SPAWNING_DELAY + 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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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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use super::*;
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