Day 11

diff --git a/src/day11.rs b/src/day11.rs
new file mode 100644 (file)
index 0000000..9ad00bd
--- /dev/null
+++ b/src/day11.rs
@@ -0,0 +1,136 @@
+use std::{str::Lines, collections::VecDeque};
+
+use itertools::Itertools;
+
+#[derive(Debug, Clone)]
+enum Operation {
+    MulOld,
+    Mul(u64),
+    Add(u64),
+}
+
+impl Operation {
+    fn parse(op: &[&str]) -> Self {
+        match op[1] {
+            "*" => if op[2] == "old" { Operation::MulOld } else { Operation::Mul(op[2].parse::<u64>().unwrap()) },
+            "+" => Operation::Add(op[2].parse::<u64>().unwrap()),
+            unknown => panic!("Unknown operation: {}", unknown),
+        }
+    }
+
+    fn apply(&self, v: u64) -> u64 {
+        match self {
+            Operation::MulOld => v * v,
+            Operation::Mul(v2) => v * v2,
+            Operation::Add(v2) => v + v2,
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct Monkey {
+    items: VecDeque<u64>,
+    operation: Operation,
+    divisible_test: u64,
+    monkey_to_throw_if_true: usize,
+    monkey_to_throw_if_false: usize,
+}
+
+static CHARS_SPLIT: &[char] = &[' ', ','];
+
+impl Monkey {
+    fn parse(lines: &mut Lines) -> Option<Self> {
+        fn split_line(s: &str) -> impl Iterator<Item = &str> {
+            s.trim().split(CHARS_SPLIT).filter(|s| !s.is_empty())
+        }
+
+        lines.next()?; // Skip first line (Monkey number).
+
+        Some(Monkey {
+            items: split_line(lines.next()?).skip(2).map(|v| v.parse::<u64>().unwrap()).collect(),
+            operation: Operation::parse(&split_line(lines.next()?).skip(3).collect::<Vec<&str>>()),
+            divisible_test: split_line(lines.next()?).nth(3).unwrap().parse::<u64>().unwrap(),
+            monkey_to_throw_if_true: split_line(lines.next()?).nth(5).unwrap().parse().unwrap(),
+            monkey_to_throw_if_false: split_line(lines.next()?).nth(5).unwrap().parse().unwrap(),
+        })
+    }
+}
+
+pub fn parse(input: &str) -> Vec<Monkey> {
+    let mut monkeys = Vec::new();
+    let mut lines = input.lines();
+    while let Some(m) = Monkey::parse(&mut lines) {
+        monkeys.push(m);
+        lines.next(); // Empty line.
+    }
+    monkeys
+}
+
+pub fn run(monkeys: &mut [Monkey], nb_rounds: u64, worry_divided: u64) -> u64 {
+    let mut inspected = vec![0u64; monkeys.len()];
+
+    let base = monkeys.iter().fold(1, |product, m| product * m.divisible_test);
+
+    for _ in 0..nb_rounds {
+        for i in 0..monkeys.len() {
+            while let Some(item) = monkeys[i].items.pop_front() {
+                inspected[i] += 1;
+                let new_worry = (monkeys[i].operation.apply(item) / worry_divided) % base;
+                if new_worry % monkeys[i].divisible_test == 0 {
+                    monkeys[monkeys[i].monkey_to_throw_if_true].items.push_back(new_worry);
+                } else {
+                    monkeys[monkeys[i].monkey_to_throw_if_false].items.push_back(new_worry);
+                }
+            }
+        }
+    }
+
+    let most_inspected_items: Vec<&u64> = inspected.iter().sorted().rev().take(2).collect();
+    most_inspected_items[0] * most_inspected_items[1]
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    static MONKEYS: &str =
+        "Monkey 0:
+         Starting items: 79, 98
+         Operation: new = old * 19
+         Test: divisible by 23
+           If true: throw to monkey 2
+           If false: throw to monkey 3
+
+         Monkey 1:
+           Starting items: 54, 65, 75, 74
+           Operation: new = old + 6
+           Test: divisible by 19
+             If true: throw to monkey 2
+             If false: throw to monkey 0
+
+         Monkey 2:
+           Starting items: 79, 60, 97
+           Operation: new = old * old
+           Test: divisible by 13
+             If true: throw to monkey 1
+             If false: throw to monkey 3
+
+         Monkey 3:
+           Starting items: 74
+           Operation: new = old + 3
+           Test: divisible by 17
+             If true: throw to monkey 0
+             If false: throw to monkey 1";
+
+    #[test]
+    fn part1() {
+        let mut monkeys = parse(MONKEYS);
+        assert_eq!(run(&mut monkeys, 20, 3), 10605);
+    }
+
+    #[test]
+    fn part2() {
+        let mut monkeys = parse(MONKEYS);
+        assert_eq!(run(&mut monkeys, 10000, 1), 2713310158);
+    }
+}
\ No newline at end of file

diff --git a/src/main.rs b/src/main.rs
index d7d6d19..0e63823 100644 (file)
--- a/src/main.rs
+++ b/src/main.rs
@@ -11,6 +11,7 @@ mod day07;
 mod day08;
 mod day09;
 mod day10;
+mod day11;
 
 fn day01() -> String {
     let f = fs::File::open("data/day01.input").unwrap();
@@ -84,6 +85,11 @@ fn day10() -> String {
     format!("part1: {}, part2: \n{}", sum_signal_strength, screen.to_ascii())
 }
 
+fn day11() -> String {
+    let monkeys = day11::parse(&fs::read_to_string("data/day11.input").unwrap());
+    format!("part1: {}, part2: {}", day11::run(&mut monkeys.clone(), 20, 3), day11::run(&mut monkeys.clone(), 10000, 1))
+}
+
 fn format_micros(t: u128) -> String {
     if t < 10_000 {
         format!("{} μs", t)
@@ -113,6 +119,7 @@ fn main() {
         day08,
         day09,
         day10,
+        day11,
     );
 
     let args: Vec<String> = env::args().skip(1).collect();