[rs] Solve 2022_11 part 1

rs/src/main.rs

@@ -61,6 +61,7 @@ days! {
     Y2022D08: "2022_08" => y2022::d08::solve,
     Y2022D09: "2022_09" => y2022::d09::solve,
     Y2022D10: "2022_10" => y2022::d10::solve,
+    Y2022D11: "2022_11" => y2022::d11::solve,
 }
 
 #[derive(Parser)]

rs/src/y2022.rs

@@ -8,3 +8,4 @@ pub mod d07;
 pub mod d08;
 pub mod d09;
 pub mod d10;
+pub mod d11;

rs/src/y2022/d11.rs

@@ -0,0 +1,126 @@
+use std::mem;
+use std::str::Lines;
+
+#[derive(Clone, Copy)]
+enum Operation {
+    Add,
+    Mul,
+}
+
+impl Operation {
+    fn eval(self, lhs: u32, rhs: u32) -> u32 {
+        match self {
+            Self::Add => lhs + rhs,
+            Self::Mul => lhs * rhs,
+        }
+    }
+}
+
+struct Monkey {
+    holds: Vec<u32>,
+
+    // Left hand side is always "old"
+    op: Operation,
+    rhs: Option<u32>,
+
+    div_by: u32,
+    if_true: usize,
+    if_false: usize,
+
+    inspections: usize,
+}
+
+impl Monkey {
+    fn parse(s: &str) -> Self {
+        let mut lines = s.lines();
+        lines.next();
+
+        fn prefixed<'a>(lines: &'a mut Lines, prefix: &str) -> &'a str {
+            lines.next().unwrap().strip_prefix(prefix).unwrap()
+        }
+
+        let holds = prefixed(&mut lines, "  Starting items: ")
+            .split(", ")
+            .map(|i| i.parse::<u32>().unwrap())
+            .collect::<Vec<_>>();
+
+        let (op, rhs) = prefixed(&mut lines, "  Operation: new = old ")
+            .split_once(' ')
+            .unwrap();
+        let op = match op {
+            "+" => Operation::Add,
+            "*" => Operation::Mul,
+            _ => panic!(),
+        };
+        let rhs = match rhs {
+            "old" => None,
+            _ => Some(rhs.parse().unwrap()),
+        };
+
+        let div_by = prefixed(&mut lines, "  Test: divisible by ")
+            .parse()
+            .unwrap();
+
+        let if_true = prefixed(&mut lines, "    If true: throw to monkey ")
+            .parse()
+            .unwrap();
+
+        let if_false = prefixed(&mut lines, "    If false: throw to monkey ")
+            .parse()
+            .unwrap();
+
+        Self {
+            holds,
+            op,
+            rhs,
+            div_by,
+            if_true,
+            if_false,
+            inspections: 0,
+        }
+    }
+
+    fn take(&mut self) -> Self {
+        Self {
+            holds: mem::take(&mut self.holds),
+            op: self.op,
+            rhs: self.rhs,
+            div_by: self.div_by,
+            if_true: self.if_true,
+            if_false: self.if_false,
+            inspections: self.inspections,
+        }
+    }
+}
+
+fn round(monkeys: &mut Vec<Monkey>) {
+    for i in 0..monkeys.len() {
+        monkeys[i].inspections += monkeys[i].holds.len();
+        let monkey = monkeys[i].take();
+        for item in monkey.holds {
+            let item = monkey.op.eval(item, monkey.rhs.unwrap_or(item)) / 3;
+            let target = if item % monkey.div_by == 0 {
+                monkey.if_true
+            } else {
+                monkey.if_false
+            };
+            monkeys[target].holds.push(item);
+        }
+    }
+}
+
+pub fn solve(input: String) {
+    let mut monkeys = vec![];
+    for monkey in input.trim().split("\n\n") {
+        monkeys.push(Monkey::parse(monkey));
+    }
+
+    for _ in 0..20 {
+        round(&mut monkeys);
+    }
+
+    let mut inspections = monkeys.iter().map(|m| m.inspections).collect::<Vec<_>>();
+    inspections.sort_unstable();
+    let part1 = inspections.into_iter().rev().take(2).product::<usize>();
+    println!("Part 1: {part1}");
+}