thallada/advent-of-code-2021
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Use rotate_left trick w/ array instead of hashmap

Browse Source
This commit is contained in:
Tyler Hallada 2021-12-06 23:59:12 -05:00
parent 36cb84d5cf
commit 4cd43547da
1 changed files with 8 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
crates/day06/src/main.rs
View File

@ -1,6 +1,5 @@
use anyhow::Result; use anyhow::Result;
use common::instrument; use common::instrument;
use std::collections::HashMap;
const INPUT: &str = include_str!("input/input.txt"); const INPUT: &str = include_str!("input/input.txt");
@ -15,20 +14,9 @@ fn simulate_day(fish: &mut Vec<u8>) {
} }
} }
fn simulate_day_with_map(fish_map: &HashMap<u8, u64>) -> HashMap<u8, u64> { fn simulate_day_with_map(fish_map: &mut [u64; 9]) {
let mut new_map = HashMap::new(); fish_map.rotate_left(1);
for (day, count) in fish_map.into_iter() { fish_map[6] += fish_map[8];
if *day == 0 {
let day8 = new_map.entry(8).or_insert(0);
*day8 += count;
let day6 = new_map.entry(6).or_insert(0);
*day6 += count;
} else {
let day_minus = new_map.entry(day - 1).or_insert(0);
*day_minus += count;
}
}
new_map
} }
fn solve_part1(input: &str) -> Result<usize> { fn solve_part1(input: &str) -> Result<usize> {
@ -52,18 +40,17 @@ fn solve_part2(input: &str) -> Result<u64> {
.map(|num| num.parse::<u8>()) .map(|num| num.parse::<u8>())
.collect::<Result<Vec<_>, std::num::ParseIntError>>()?; .collect::<Result<Vec<_>, std::num::ParseIntError>>()?;
let mut fish_map: HashMap<u8, u64> = HashMap::new(); let mut fish_map = [0; 9];
for f in fish.iter() { for f in fish.into_iter() {
let count = fish_map.entry(*f).or_insert(0); fish_map[f as usize] += 1;
*count += 1;
} }
for _ in 0..256 { for _ in 0..256 {
fish_map = simulate_day_with_map(&fish_map); simulate_day_with_map(&mut fish_map);
} }
Ok(fish_map.values().sum()) Ok(fish_map.iter().sum())
} }
fn main() { fn main() {