Implement day 07 part 1.

2018/inputs/07.txt

@@ -0,0 +1,101 @@
+Step Q must be finished before step O can begin.
+Step Z must be finished before step G can begin.
+Step W must be finished before step V can begin.
+Step C must be finished before step X can begin.
+Step O must be finished before step E can begin.
+Step K must be finished before step N can begin.
+Step P must be finished before step I can begin.
+Step X must be finished before step D can begin.
+Step N must be finished before step E can begin.
+Step F must be finished before step A can begin.
+Step U must be finished before step Y can begin.
+Step M must be finished before step H can begin.
+Step J must be finished before step B can begin.
+Step B must be finished before step E can begin.
+Step S must be finished before step L can begin.
+Step A must be finished before step L can begin.
+Step E must be finished before step L can begin.
+Step L must be finished before step G can begin.
+Step D must be finished before step I can begin.
+Step Y must be finished before step I can begin.
+Step I must be finished before step G can begin.
+Step G must be finished before step R can begin.
+Step V must be finished before step T can begin.
+Step R must be finished before step H can begin.
+Step H must be finished before step T can begin.
+Step S must be finished before step E can begin.
+Step C must be finished before step E can begin.
+Step P must be finished before step T can begin.
+Step I must be finished before step H can begin.
+Step O must be finished before step P can begin.
+Step M must be finished before step L can begin.
+Step S must be finished before step D can begin.
+Step P must be finished before step D can begin.
+Step P must be finished before step R can begin.
+Step I must be finished before step R can begin.
+Step Y must be finished before step G can begin.
+Step Q must be finished before step L can begin.
+Step N must be finished before step R can begin.
+Step J must be finished before step E can begin.
+Step N must be finished before step T can begin.
+Step B must be finished before step V can begin.
+Step Q must be finished before step B can begin.
+Step J must be finished before step H can begin.
+Step F must be finished before step B can begin.
+Step W must be finished before step X can begin.
+Step S must be finished before step T can begin.
+Step J must be finished before step G can begin.
+Step O must be finished before step R can begin.
+Step K must be finished before step B can begin.
+Step Z must be finished before step O can begin.
+Step Q must be finished before step S can begin.
+Step K must be finished before step V can begin.
+Step B must be finished before step R can begin.
+Step J must be finished before step T can begin.
+Step E must be finished before step T can begin.
+Step G must be finished before step V can begin.
+Step D must be finished before step Y can begin.
+Step M must be finished before step Y can begin.
+Step F must be finished before step G can begin.
+Step C must be finished before step P can begin.
+Step V must be finished before step R can begin.
+Step R must be finished before step T can begin.
+Step J must be finished before step Y can begin.
+Step U must be finished before step R can begin.
+Step Z must be finished before step F can begin.
+Step Q must be finished before step V can begin.
+Step U must be finished before step M can begin.
+Step J must be finished before step R can begin.
+Step L must be finished before step V can begin.
+Step W must be finished before step K can begin.
+Step B must be finished before step Y can begin.
+Step O must be finished before step N can begin.
+Step D must be finished before step V can begin.
+Step P must be finished before step B can begin.
+Step U must be finished before step I can begin.
+Step O must be finished before step T can begin.
+Step S must be finished before step G can begin.
+Step X must be finished before step A can begin.
+Step U must be finished before step T can begin.
+Step A must be finished before step I can begin.
+Step B must be finished before step G can begin.
+Step N must be finished before step Y can begin.
+Step Z must be finished before step J can begin.
+Step M must be finished before step D can begin.
+Step U must be finished before step A can begin.
+Step S must be finished before step R can begin.
+Step Z must be finished before step A can begin.
+Step Y must be finished before step R can begin.
+Step E must be finished before step Y can begin.
+Step N must be finished before step G can begin.
+Step Z must be finished before step X can begin.
+Step P must be finished before step X can begin.
+Step Z must be finished before step T can begin.
+Step Z must be finished before step P can begin.
+Step V must be finished before step H can begin.
+Step P must be finished before step L can begin.
+Step L must be finished before step H can begin.
+Step X must be finished before step V can begin.
+Step W must be finished before step G can begin.
+Step N must be finished before step D can begin.
+Step Z must be finished before step U can begin.

2018/src/day07.rs

@@ -0,0 +1,87 @@
+use std::cmp::Reverse;
+use std::collections::HashMap;
+use std::io::BufRead;
+use std::io::BufReader;
+use std::io::Read;
+
+use regex::Regex;
+
+use common::Solution;
+use std::collections::HashSet;
+use std::collections::BinaryHeap;
+
+fn append_edge(target: &mut HashMap<char, Vec<char>>, source: char, dest: char) {
+    target.entry(source).or_insert(Vec::new()).push(dest);
+}
+
+#[derive(Default, Debug)]
+pub struct Day07 {
+    forward: HashMap<char, Vec<char>>,
+    backward: HashMap<char, Vec<char>>,
+}
+
+impl Day07 {
+    pub fn new() -> Self {
+        Default::default()
+    }
+
+    fn read_edges(&mut self, input: &mut Read) {
+        let reader = BufReader::new(input);
+        let regex = Regex::new(r"Step (\w) must be finished before step (\w) can begin").unwrap();
+
+        for line in reader.lines() {
+            let line = line.unwrap();
+            let groups = regex.captures(&line).unwrap();
+            let a = groups[1].chars().next().unwrap();
+            let b = groups[2].chars().next().unwrap();
+
+            append_edge(&mut self.forward, a, b);
+            append_edge(&mut self.backward, b, a);
+        }
+    }
+}
+
+impl Solution for Day07 {
+    fn part1(&mut self, input: &mut Read) -> String {
+        self.read_edges(input);
+
+        let mut result = String::new();
+        let mut finished = HashSet::new();
+
+        let mut starting_points: BinaryHeap<Reverse<char>> = self.forward.keys().filter(|&x| !self.backward.contains_key(x))
+            .map(|&x| Reverse(x)).collect();
+
+        while let Some(Reverse(c)) = starting_points.pop() {
+            result.push(c);
+            finished.insert(c);
+
+            if let Some(dependents) = self.forward.get(&c) {
+                for d in dependents {
+                    if self.backward.get(d).unwrap().iter().all(|x| finished.contains(x)) {
+                        starting_points.push(Reverse(*d));
+                    }
+                }
+            }
+        }
+
+        result
+    }
+
+    fn part2(&mut self, input: &mut Read) -> String {
+        unimplemented!()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use common::Solution;
+    use day07::Day07;
+
+    const SAMPLE_INPUT: &[u8] = include_bytes!("samples/07.txt");
+
+    #[test]
+    pub fn sample_part1() {
+        let mut instance = Day07::new();
+        assert_eq!("CABDFE", instance.part1(&mut SAMPLE_INPUT));
+    }
+}

2018/src/main.rs

@@ -16,6 +16,7 @@ pub mod day03;
 pub mod day04;
 pub mod day05;
 pub mod day06;
+pub mod day07;
 
 fn get_impl(day: &str) -> Box<common::Solution> {
     match day.parse() {
@@ -25,6 +26,7 @@ fn get_impl(day: &str) -> Box<common::Solution> {
         Ok(4) => Box::new(day04::Day04::new()),
         Ok(5) => Box::new(day05::Day05::new()),
         Ok(6) => Box::new(day06::Day06::new()),
+        Ok(7) => Box::new(day07::Day07::new()),
         Ok(val) => panic!("Unimplemented day {}", val),
         _ => panic!("Invalid number"),
     }

2018/src/samples/07.txt

@@ -0,0 +1,7 @@
+Step C must be finished before step A can begin.
+Step C must be finished before step F can begin.
+Step A must be finished before step B can begin.
+Step A must be finished before step D can begin.
+Step B must be finished before step E can begin.
+Step D must be finished before step E can begin.
+Step F must be finished before step E can begin.