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use std::collections::{BTreeMap, HashMap, HashSet};
const INPUT: &str = include_str!("../../data/day21");
struct FoodDescription<'a> {
ingredients: HashSet<&'a str>,
allergens: HashSet<&'a str>,
}
impl<'a> FoodDescription<'a> {
fn parse(line: &'a str) -> Self {
let pos = line.find(" (contains ").unwrap();
let ingredients = &line[..pos];
let allergens = line[pos..].strip_prefix(" (contains ").unwrap().strip_suffix(")").unwrap();
FoodDescription {
ingredients: ingredients.split_whitespace().collect(),
allergens: allergens.split(", ").collect(),
}
}
}
fn main() {
let fds = INPUT.lines().map(FoodDescription::parse).collect::<Vec<_>>();
let allergens: HashSet<&str> = fds.iter().map(|fd| fd.allergens.iter().cloned()).flatten().collect();
let mut allergen_map_poss: HashMap<&str, HashSet<&str>> = allergens.iter().map(|&a| {
let mut is = fds.iter()
.filter(|fd| fd.allergens.contains(a))
.map(|fd| &fd.ingredients);
let first_ingr: HashSet<&str> = is.next().unwrap().clone();
let poss = is.fold(first_ingr, |memo, ingr| {
memo.intersection(ingr).cloned().collect::<HashSet<_>>()
});
(a, poss)
}).collect();
let mut allergen_map: BTreeMap<&str, &str> = BTreeMap::new();
while !allergen_map_poss.is_empty() {
let (next_allg, next_ingr) = allergen_map_poss.iter().filter_map(|(&a, is)| {
if is.len() == 1 {
Some((a, *is.iter().next().unwrap()))
} else {
None
}
}).next().unwrap();
allergen_map.insert(next_allg, next_ingr);
allergen_map_poss.remove(next_allg);
for ingr in allergen_map_poss.values_mut() {
ingr.remove(next_ingr);
}
}
println!("Allergens contained by ingredients: {:?}", allergen_map);
let all_ingredients: HashSet<&str> = allergen_map.values().cloned().collect();
println!(
"Ingredients not allergens used {} times",
fds.iter().map(|fd| fd.ingredients.difference(&all_ingredients).count()).sum::<usize>(),
);
println!("Dangerous ingredients: {}", allergen_map.values().cloned().collect::<Vec<_>>().join(","));
}