day 11

Cargo.toml

@@ -11,4 +11,5 @@ members = [
     "day8",
     "day9",
     "day10",
+    "day11",
 ]

day11/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "day11"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+num = { version = "0.4.0" }

day11/input.txt

@@ -0,0 +1,55 @@
+Monkey 0:
+  Starting items: 89, 74
+  Operation: new = old * 5
+  Test: divisible by 17
+    If true: throw to monkey 4
+    If false: throw to monkey 7
+
+Monkey 1:
+  Starting items: 75, 69, 87, 57, 84, 90, 66, 50
+  Operation: new = old + 3
+  Test: divisible by 7
+    If true: throw to monkey 3
+    If false: throw to monkey 2
+
+Monkey 2:
+  Starting items: 55
+  Operation: new = old + 7
+  Test: divisible by 13
+    If true: throw to monkey 0
+    If false: throw to monkey 7
+
+Monkey 3:
+  Starting items: 69, 82, 69, 56, 68
+  Operation: new = old + 5
+  Test: divisible by 2
+    If true: throw to monkey 0
+    If false: throw to monkey 2
+
+Monkey 4:
+  Starting items: 72, 97, 50
+  Operation: new = old + 2
+  Test: divisible by 19
+    If true: throw to monkey 6
+    If false: throw to monkey 5
+
+Monkey 5:
+  Starting items: 90, 84, 56, 92, 91, 91
+  Operation: new = old * 19
+  Test: divisible by 3
+    If true: throw to monkey 6
+    If false: throw to monkey 1
+
+Monkey 6:
+  Starting items: 63, 93, 55, 53
+  Operation: new = old * old
+  Test: divisible by 5
+    If true: throw to monkey 3
+    If false: throw to monkey 1
+
+Monkey 7:
+  Starting items: 50, 61, 52, 58, 86, 68, 97
+  Operation: new = old + 4
+  Test: divisible by 11
+    If true: throw to monkey 5
+    If false: throw to monkey 4

day11/sample_input.txt

@@ -0,0 +1,27 @@
+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

day11/src/main.rs

@@ -0,0 +1,115 @@
+struct Monkey {
+    items: Vec<i64>,
+    operation: Box<dyn Fn(i64) -> i64>,
+    test: Box<dyn Fn(i64) -> i64>,
+    inspections: u64,
+}
+
+fn empty_op(_: i64) -> i64 {
+    -1
+}
+
+fn empty_test(_: i64) -> i64 {
+    -1
+}
+
+fn op_func(op: char, operand: &str) -> Box<dyn Fn(i64) -> i64> {
+    let op = match op {
+        '*' => std::ops::Mul::mul,
+        '+' => std::ops::Add::add,
+        _   => panic!("unsupported op {}", op),
+    };
+    if operand == "old" {
+        Box::new(move |x| {
+            op(x, x)
+        })
+    } else {
+        let operand: i64 = operand.parse().unwrap();
+        Box::new(move |x| {
+            op(x, operand)
+        })
+    }
+}
+
+fn main() {
+    const INPUT: &str = include_str!("../input.txt");
+
+    let mut monkeys: Vec<Monkey> = Vec::new();
+    
+    let mut cur_monkey = -1i64;
+    let mut cur_test_divisor = -1i64;
+    let mut cur_test_true_ret = -1i64;
+
+    let mut lcm: i64 = 1;
+
+    for line in INPUT.lines() {
+        let line = line.trim_start();
+
+        if line == "" {
+            continue;
+        }
+        else if line.starts_with("Monkey") {
+            cur_monkey += 1;
+            monkeys.push(Monkey {
+                items: Vec::new(),
+                operation: Box::new(empty_op),
+                test: Box::new(empty_test),
+                inspections: 0
+            });
+            continue;
+        }
+        else if line.starts_with("Starting items: ") {
+            let items = line[16..].split(", ");
+            for item in items {
+                monkeys[cur_monkey as usize].items.push(item.parse().unwrap());
+            }
+        }
+        else if line.starts_with("Operation: ") {
+            let mut items = line[21..].split(' ');
+            let op = items.next().unwrap().chars().next().unwrap();
+            let operand = items.next().unwrap();
+
+            monkeys[cur_monkey as usize].operation = op_func(op, operand);
+        }
+        else if line.starts_with("Test: ") {
+            cur_test_divisor = line[19..].parse().unwrap();
+            lcm = num::integer::lcm(lcm, cur_test_divisor);
+        }
+        else if line.starts_with("If true: ") {
+            cur_test_true_ret = line[25..].parse().unwrap();
+        }
+        else if line.starts_with("If false: ") {
+            let target: i64 = line[26..].parse().unwrap();
+
+            monkeys[cur_monkey as usize].test = Box::new(move |x| {
+                if x % cur_test_divisor == 0 {
+                    cur_test_true_ret
+                } else {
+                    target
+                }
+            });
+        }
+    }
+
+    println!("lcm: {}", lcm);
+
+    for _ in 1..=10000 {
+        for i in 0..monkeys.len() {
+            for j in 0..monkeys[i].items.len() {
+                let mut new_worry = (monkeys[i].operation)(monkeys[i].items[j]);
+                new_worry = new_worry % lcm;
+                let dest: usize = (monkeys[i].test)(new_worry).try_into().unwrap();
+
+                monkeys[dest].items.push(new_worry);
+                monkeys[i].inspections += 1;
+            }
+            monkeys[i].items.clear();
+        }
+    }
+
+    let mut active_monkeys = monkeys.iter().map(|m| { m.inspections }).collect::<Vec<u64>>();
+    active_monkeys.sort();
+    active_monkeys.reverse();
+
+    println!("{}", active_monkeys[0] * active_monkeys[1]);
+}