2022 Day 5

2022/src/bin/day05.rs

@@ -0,0 +1,108 @@
+use regex::Regex;
+
+const INPUT: &str = include_str!("../../input/day05.txt");
+
+fn main() {
+    println!("{}", part1(INPUT));
+    println!("{}", part2(INPUT));
+}
+
+type Crate = String;
+
+type Stack = Vec<Crate>;
+
+#[derive(Debug, Clone)]
+struct Ship {
+    stacks: Vec<Stack>,
+}
+
+impl Ship {
+    fn parse(input: &str) -> Self {
+        let lines: Vec<&str> = input.trim().split('\n').rev().collect();
+
+        let mut ship = Ship {
+            stacks: (0..=8).map(|_| Vec::new()).collect(),
+        };
+
+        for line in &lines[1..] {
+            for stk in 0..=8 {
+                let i = 4 * stk + 1;
+                let contents = match line.get(i..i + 1) {
+                    None => continue,
+                    Some(" ") => continue,
+                    Some(contents) => contents,
+                };
+                ship.stacks[stk].push(contents.to_string());
+            }
+        }
+
+        ship
+    }
+
+    fn do_move_1(&mut self, m: Move) {
+        for _ in 0..(m.count) {
+            let item = self.stacks[m.from].pop().expect("must have item");
+            self.stacks[m.to].push(item);
+        }
+    }
+
+    fn do_move_2(&mut self, m: Move) {
+        let src = &mut self.stacks[m.from];
+        let items = src.split_off(src.len() - m.count);
+        self.stacks[m.to].extend(items.to_vec());
+    }
+
+    fn tops(&self) -> String {
+        let mut s = String::new();
+        for stk in &self.stacks {
+            s += stk.last().unwrap();
+        }
+        s
+    }
+}
+
+#[derive(Debug, Copy, Clone)]
+struct Move {
+    count: usize,
+    from: usize,
+    to: usize,
+}
+
+impl Move {
+    fn parse(line: &str) -> Self {
+        let re = Regex::new(r"^move (\d+) from (\d+) to (\d+)$").unwrap();
+        let caps = re.captures(line).unwrap();
+
+        Self {
+            count: caps[1].parse().unwrap(),
+            from: caps[2].parse::<usize>().unwrap() - 1, // zero-index
+            to: caps[3].parse::<usize>().unwrap() - 1,   // zero-index
+        }
+    }
+}
+
+fn part1(input: &str) -> String {
+    let sections: Vec<&str> = input.split("\n\n").collect();
+
+    let mut ship = Ship::parse(sections[0]);
+    let moves: Vec<Move> = sections[1].trim().split('\n').map(Move::parse).collect();
+
+    for m in moves {
+        ship.do_move_1(m);
+    }
+
+    ship.tops()
+}
+
+fn part2(input: &str) -> String {
+    let sections: Vec<&str> = input.split("\n\n").collect();
+
+    let mut ship = Ship::parse(sections[0]);
+    let moves: Vec<Move> = sections[1].trim().split('\n').map(Move::parse).collect();
+
+    for m in moves {
+        ship.do_move_2(m);
+    }
+
+    ship.tops()
+}