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use {
anyhow::{
anyhow,
Context,
Result,
},
std::{
env::args,
fs::File,
io::{
BufRead,
BufReader,
},
path::Path,
},
};
fn read_input<T: AsRef<Path>>(filename: T) -> Result<Vec<Vec<usize>>> {
let reader = BufReader::new(File::open(filename)?);
let mut elves = vec![vec![]];
for line in reader.lines() {
let s = line?;
if s.is_empty() {
elves.push(vec![]);
continue;
}
let elf = elves.last_mut().context("Invalid elves vector.")?;
let n = s.parse().context("Could not parse {s}")?;
elf.push(n);
}
Ok(elves)
}
fn part1<'a, I: IntoIterator<Item = &'a Vec<usize>>>(input: I) -> Result<usize> {
input.into_iter().map(|foodpacks| foodpacks.iter().sum()).max()
.context("Iterator chain in first part failed.")
}
fn part2<'a, I: IntoIterator<Item = &'a Vec<usize>>>(input: I) -> Result<usize> {
let mut calories: Vec<usize> = input.into_iter().map(|foodpacks| foodpacks.iter().sum())
.collect();
calories.sort();
Ok(calories.into_iter().rev().take(3).sum::<usize>())
}
fn main() -> Result<()> {
let ( do_part_1, do_part_2 ) = aoc::do_parts();
let filename = args().nth(1).ok_or_else(|| anyhow!("Missing input filename"))?;
let input = read_input(filename).context("Could not read input")?;
if do_part_1 {
let solution = part1(&input).context("No solution for part 1")?;
println!("Part1, solution found to be: {}", solution);
}
if do_part_2 {
let solution = part2(&input).context("No solution for part 2")?;
println!("Part2, solution found to be: {}", solution);
}
Ok(())
}
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