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use std::io;
use std::io::BufRead;
use std::cmp::Ordering;
use std::collections::BinaryHeap;
#[derive(PartialEq, Eq)]
struct DecreasingU8(u8);
impl PartialOrd for DecreasingU8 {
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
Some(self.cmp(other))
}
}
impl Ord for DecreasingU8 {
fn cmp(&self, other: &Self) -> Ordering {
other.0.cmp(&self.0)
}
}
fn simulation(nexts: &[Vec<u8>], nelves: i32, basetime: i32, inctime: i32) -> (String, i32) {
let mut incoming = [0; 26];
for tos in nexts.iter() {
for &to in tos {
incoming[to as usize] += 1;
}
}
let mut sources = BinaryHeap::new();
for i in 0..26 {
if incoming[i as usize] == 0 {
sources.push(DecreasingU8(i));
}
}
let mut order = String::new();
while sources.len() > 0 {
let DecreasingU8(i) = sources.pop().unwrap();
order.push(char::from(i + 65));
for &to in &nexts[i as usize] {
incoming[to as usize] -= 1;
if incoming[to as usize] == 0 {
sources.push(DecreasingU8(to));
}
}
}
(order, 0)
}
pub fn main<T: BufRead>(reader: T) -> io::Result<(String, String)> {
let mut nexts: Vec<Vec<u8>> = vec![vec![]; 26];
for l in reader.lines().map(|l| l.unwrap()) {
let (from, to) = (l.as_bytes()[5] - 65, l.as_bytes()[36] - 65);
nexts[from as usize].push(to);
}
let (part1, _) = simulation(&nexts, 1, 1, 0);
Ok((part1, String::new()))
}
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