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use std::collections::{HashMap, HashSet};
use std::io::{self, Read};
fn solve1(input: &str) -> usize {
let mut pipes: HashMap<u32, Vec<u32>> = HashMap::new();
for line in input.lines() {
let mut words = line.split_whitespace();
let src = words.next().unwrap().parse().unwrap();
assert_eq!(Some("<->"), words.next());
for dest in words {
let dest = dest.trim_right_matches(',').parse().unwrap();
pipes.entry(src).or_insert(vec![]).push(dest);
pipes.entry(dest).or_insert(vec![]).push(src);
}
}
let mut group = HashSet::new();
group.insert(0);
let mut prev = None;
while Some(group.len()) != prev {
prev = Some(group.len());
for (src, dests) in &pipes {
if group.contains(src) {
group.extend(dests);
}
}
}
group.len()
}
fn main() {
let mut input = String::new();
io::stdin().read_to_string(&mut input).unwrap();
println!("Part 1: {}", solve1(&input));
}
#[test]
fn part1() {
assert_eq!(6, solve1(
"\
0 <-> 2
1 <-> 1
2 <-> 0, 3, 4
3 <-> 2, 4
4 <-> 2, 3, 6
5 <-> 6
6 <-> 4, 5
"
));
}
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