Solution for 2021: day 6

Dependencies

• [2] M2AJCSV3 Solution for 2021 day 5
• [3] M7EGDCFH Remove unused code
• [*] HUHAFQLN 2021 day 1
• [*] TNWJK3WA Apply cargo clippy

Change contents

• file addition: day6.rs (----------)
  [5.16]
  + fn main() {

  + use std::io::BufRead;

  + let mut pops: [u128; 9] = [0; 9];

  + let filename = std::env::args().nth(1).expect("Expected filename");

  + let file = std::io::BufReader::new(

  + std::fs::File::open(<String as AsRef<std::path::Path>>::as_ref(

  + &filename,

  + ))

  + .unwrap(),

  + );

  + for i in file.split(b',') {

  + let i: usize = std::str::from_utf8(&i.unwrap())

  + .unwrap()

  + .trim()

  + .parse()

  + .unwrap();

  + pops[i] += 1;

  + }

  + for g in 1..=256 {

  + let mut next: [u128; 9] = [0; 9];

  + for (i, p) in pops.iter().enumerate() {

  + for j in advance_lanternfish(i as u8) {

  + next[j as usize] += p;

  + }

  + }

  + pops = next;

  + if g == 80 || g == 256 {

  + println!("Day {}: {}", g, pops.iter().sum::<u128>());

  + }

  + }

  + }

  +

  + fn advance_lanternfish(timer: u8) -> Box<dyn Iterator<Item = u8>> {

  + use std::iter::once;

  + if timer == 0 {

  + Box::new(once(6).chain(once(8)))

  + } else {

  + Box::new(once(timer - 1))

  + }

  + }
• edit in 2021/day5.rs at line 136
  [2.4161]→[2.4161:4162](∅→∅)
  −
• edit in 2021/Cargo.toml at line 30
  [6.1457]
  + [[bin]]

  + name = "day6"

  + path = "day6.rs"