day07-1

src/tasks/day07.rs

@@ -0,0 +1,42 @@
+use crate::utils;
+use std::collections::{HashMap, HashSet};
+
+pub fn task1() {
+    let input = utils::read_file("input/day07.txt");
+    let mut tasks: HashSet<char> = HashSet::new();
+    let dependencies: Vec<(char, char)> = input
+        .lines()
+        .map(|line| (line.chars().nth(5).unwrap(), line.chars().nth(36).unwrap()))
+        .collect();
+
+    let mut depends_on: HashMap<char, HashSet<char>> = HashMap::new();
+    for (a, b) in dependencies {
+        depends_on.entry(b).or_insert(HashSet::new()).insert(a);
+        tasks.insert(a);
+        tasks.insert(b);
+    }
+
+    let mut open: HashSet<char> = tasks
+        .iter()
+        .filter(|task| !depends_on.contains_key(task))
+        .map(|c| *c)
+        .collect();
+
+    let mut result = String::new();
+    while open.len() > 0 {
+        let next = open.iter().min().unwrap().clone();
+        open.remove(&next);
+        result.push(next);
+        let newly_open: HashSet<char> = depends_on
+            .iter()
+            .filter(|(task, deps)| deps.iter().all(|dep| result.chars().any(|c| c == *dep)))
+            .map(|(task, _)| *task)
+            .collect();
+        open = open.union(&newly_open).map(|c| *c).collect();
+        for c in newly_open {
+            depends_on.remove(&c);
+        }
+    }
+
+    println!("{}", result);
+}