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use anyhow::Result;
use std::collections::HashMap;
use std::env::args;
use std::fs::File;
use std::io::{BufRead, BufReader};
use std::path::Path;
fn read_input<T: AsRef<Path>>(filename: T) -> Result<Vec<usize>> {
let f = File::open(filename)?;
let reader = BufReader::new(f);
let values = reader.lines()
.map(|v| v?.parse::<usize>().map_err(anyhow::Error::new)).collect();
values
}
fn part1(input: &[usize]) -> Option<usize> {
let mut sorted = input.to_vec();
sorted.push(0);
sorted.sort();
let max = sorted[sorted.len()-1];
sorted.push(max+3);
let (_prev, count) = sorted.iter().fold((None, vec![0, 0, 0, 0]), |acc, jolt| {
let mut res = acc.1.clone();
if let Some(prev) = acc.0 {
let diff = jolt - prev;
res[diff] += 1;
}
(Some(jolt), res)
});
Some(count[1] * count[3])
}
fn part2(input: &[usize]) -> Option<u128> {
let mut sorted = input.to_vec();
sorted.push(0);
sorted.sort();
let max = sorted[sorted.len()-1];
sorted.push(max+3);
let mut paths: HashMap<usize, u128> = HashMap::new();
paths.insert(max+3, 1);
sorted.iter().rev().fold(0, |_, elem| {
let count = (1..=3).map(|jump| {
let pos = *elem + jump;
if sorted.contains(&pos) {
paths.get(&pos).copied().unwrap_or(0)
} else {
0
}
}).sum();
let lm = paths.entry(*elem).or_insert(0);
*lm += count;
count
});
Some(paths[&0])
}
fn main() {
let ( do_part_1, do_part_2 ) = aoc::do_parts();
let filename = match args().nth(1) {
Some(f) => f,
None => {
eprintln!("Missing input filename");
std::process::exit(1);
},
};
match read_input(filename) {
Ok(input) => {
if do_part_1 {
match part1(&input) {
Some(solution) => println!("Part1: {}", solution),
None => {
eprintln!("Part1, no solution found");
std::process::exit(1);
}
};
}
if do_part_2 {
match part2(&input) {
Some(solution) => println!("Part2: {}", solution),
None => {
eprintln!("Part2, no solution found");
std::process::exit(1);
}
};
}
},
Err(err) => eprintln!("Could not read input: {}", err),
}
}
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