1
Fork 0
advent-of-code/source/day_06/mod.rs

73 lines
1.5 KiB
Rust
Raw Normal View History

2021-12-06 11:16:13 +00:00
use std::collections::HashMap;
use color_eyre::Result;
type FishMap = HashMap<isize, isize>;
pub fn solve() -> Result<()> {
let input_data = include_str!("../../data/day_06.txt").trim();
println!("Day 06 Part 1: {}", part_1(input_data)?);
println!("Day 06 Part 2: {}", part_2(input_data)?);
Ok(())
}
fn part_1(input: &str) -> Result<isize> {
let mut fishes = parse_fishes(input)?;
for _ in 0..80 {
fishes = simulate_fishes(fishes);
}
Ok(count_fishes(fishes))
}
fn part_2(input: &str) -> Result<isize> {
let mut fishes = parse_fishes(input)?;
for _ in 0..256 {
fishes = simulate_fishes(fishes);
}
Ok(count_fishes(fishes))
}
fn parse_fishes(input: &str) -> Result<FishMap> {
let mut fishes = FishMap::new();
let individual_fishes = input
.split(",")
.map(str::parse)
.collect::<Result<Vec<_>, _>>()?;
for fish in individual_fishes {
let amount = fishes.entry(fish).or_default();
*amount += 1;
}
Ok(fishes)
}
fn count_fishes(fishes: FishMap) -> isize {
fishes.into_iter().map(|(_, amount)| amount).sum()
}
fn simulate_fishes(fishes: FishMap) -> FishMap {
let mut new_fishes = HashMap::new();
for (mut timer, amount) in fishes {
timer -= 1;
if timer < 0 {
let new_fish = new_fishes.entry(8).or_default();
*new_fish += amount;
let reset_fish = new_fishes.entry(6).or_default();
*reset_fish += amount;
} else {
let current_fish = new_fishes.entry(timer).or_default();
*current_fish += amount;
}
}
new_fishes
}