Day 11

day11/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day11"
+version = "0.1.0"

day11/input.txt

@@ -0,0 +1,55 @@
+Monkey 0:
+  Starting items: 84, 66, 62, 69, 88, 91, 91
+  Operation: new = old * 11
+  Test: divisible by 2
+    If true: throw to monkey 4
+    If false: throw to monkey 7
+
+Monkey 1:
+  Starting items: 98, 50, 76, 99
+  Operation: new = old * old
+  Test: divisible by 7
+    If true: throw to monkey 3
+    If false: throw to monkey 6
+
+Monkey 2:
+  Starting items: 72, 56, 94
+  Operation: new = old + 1
+  Test: divisible by 13
+    If true: throw to monkey 4
+    If false: throw to monkey 0
+
+Monkey 3:
+  Starting items: 55, 88, 90, 77, 60, 67
+  Operation: new = old + 2
+  Test: divisible by 3
+    If true: throw to monkey 6
+    If false: throw to monkey 5
+
+Monkey 4:
+  Starting items: 69, 72, 63, 60, 72, 52, 63, 78
+  Operation: new = old * 13
+  Test: divisible by 19
+    If true: throw to monkey 1
+    If false: throw to monkey 7
+
+Monkey 5:
+  Starting items: 89, 73
+  Operation: new = old + 5
+  Test: divisible by 17
+    If true: throw to monkey 2
+    If false: throw to monkey 0
+
+Monkey 6:
+  Starting items: 78, 68, 98, 88, 66
+  Operation: new = old + 6
+  Test: divisible by 11
+    If true: throw to monkey 2
+    If false: throw to monkey 5
+
+Monkey 7:
+  Starting items: 70
+  Operation: new = old + 7
+  Test: divisible by 5
+    If true: throw to monkey 1
+    If false: throw to monkey 3

day11/src/main.rs

@@ -1,3 +1,426 @@
-fn main() {
-    println!("Hello, world!");
+use std::{
+    cmp::{Ordering, Reverse},
+    fs::read_to_string,
+    io::Write,
+    ops::{Add, Div, Mul, Rem, Shl, Sub},
+    rc::Rc,
+    str::Lines,
+};
+
+#[derive(Debug, Clone)]
+struct BigInt {
+    numbers: Vec<u64>,
+}
+
+impl From<i32> for BigInt {
+    fn from(int: i32) -> Self {
+        Self {
+            numbers: vec![int as u64],
+        }
+    }
+}
+
+impl From<u64> for BigInt {
+    fn from(int: u64) -> Self {
+        Self { numbers: vec![int] }
+    }
+}
+
+impl From<u128> for BigInt {
+    fn from(int: u128) -> Self {
+        let lower = ((int << 64) >> 64) as u64;
+        let higher = (int >> 64) as u64;
+        Self {
+            numbers: vec![lower, higher],
+        }
+        .shrink()
+    }
+}
+
+impl Add<BigInt> for BigInt {
+    type Output = BigInt;
+
+    fn add(self, rhs: BigInt) -> Self::Output {
+        let (mut output, other) = if self.numbers.len() > rhs.numbers.len() {
+            (self, rhs)
+        } else {
+            (rhs, self)
+        };
+        let mut carry = false;
+        let mut shortest_length = other.numbers.len();
+        for i in 0..shortest_length {
+            let new_carry;
+            (output.numbers[i], new_carry) = output.numbers[i].overflowing_add(other.numbers[i]);
+            if carry {
+                (output.numbers[i], carry) = output.numbers[i].overflowing_add(1);
+            }
+            carry = new_carry || carry;
+        }
+        while carry {
+            if output.numbers.len() == shortest_length {
+                output.numbers.push(0);
+            }
+            (output.numbers[shortest_length], carry) =
+                output.numbers[shortest_length].overflowing_add(1);
+            shortest_length += 1;
+        }
+        output.shrink()
+    }
+}
+
+impl Sub for BigInt {
+    type Output = BigInt;
+
+    fn sub(self, other: Self) -> Self::Output {
+        let mut s = self;
+        if s < other {
+            panic!("cannot subtract bigger number from smaller number");
+        }
+        let mut carry = false;
+        for i in (0..other.numbers.len()).rev() {
+            let new_carry;
+            (s.numbers[i], new_carry) = s.numbers[i].overflowing_sub(other.numbers[i]);
+            if carry {
+                (s.numbers[i], carry) = s.numbers[i].overflowing_sub(1);
+            }
+            carry = new_carry || carry;
+        }
+        s.shrink()
+    }
+}
+
+impl Mul for BigInt {
+    type Output = BigInt;
+
+    fn mul(self, other: Self) -> Self::Output {
+        let mut output: Self = 0.into();
+        for &digit in other.numbers.iter().rev() {
+            output = (output << 64) + (digit * self.clone());
+        }
+        output.shrink()
+    }
+}
+
+impl Mul<BigInt> for u64 {
+    type Output = BigInt;
+
+    fn mul(self, rhs: BigInt) -> Self::Output {
+        let mut output: BigInt = 0.into();
+        for &digit in rhs.numbers.iter().rev() {
+            output = (output << 64) + (digit as u128 * self as u128).into();
+        }
+        output.shrink()
+    }
+}
+
+impl BigInt {
+    fn div_rem(self, other: Self) -> (Self, Self) {
+        let mut q: Self = Self {
+            numbers: vec![0; self.numbers.len()],
+        };
+        let mut r: Self = 0.into();
+        for i in (0..(self.numbers.len() * 64)).rev() {
+            r = r << 1;
+            let bit_index = i / 64;
+            let bit = i % 64;
+            r.numbers[0] |= u64::from(self.numbers[bit_index] & (1 << bit) != 0);
+            if r >= other.clone() {
+                r = r - other.clone();
+                q.numbers[bit_index] |= 1 << bit;
+            }
+        }
+        (q.shrink(), r.shrink())
+    }
+
+    fn shrink(self) -> Self {
+        let mut s = self;
+        for i in (1..s.numbers.len()).rev() {
+            if s.numbers[i] == 0 {
+                s.numbers.pop();
+            } else {
+                break;
+            }
+        }
+        s
+    }
+}
+
+impl Div for BigInt {
+    type Output = BigInt;
+
+    fn div(self, other: Self) -> Self::Output {
+        let (div, _) = self.div_rem(other);
+        div
+    }
+}
+
+impl Rem for BigInt {
+    type Output = BigInt;
+
+    fn rem(self, other: Self) -> Self::Output {
+        let (_, rem) = self.div_rem(other);
+        rem
+    }
+}
+
+impl Shl<usize> for BigInt {
+    type Output = BigInt;
+
+    fn shl(self, rhs: usize) -> Self::Output {
+        let mut output = self.clone();
+        let q = rhs / 64;
+        let r = rhs % 64;
+        output.numbers.push(0);
+        for i in (1..self.numbers.len()).rev() {
+            output.numbers[i] <<= r;
+            output.numbers[i] |= output.numbers[i] >> (64 - 4);
+        }
+        output.numbers[0] <<= r;
+        for _ in 0..q {
+            output.numbers.push(0);
+            for i in (1..output.numbers.len()).rev() {
+                output.numbers[i] = output.numbers[i - 1];
+            }
+            output.numbers[0] = 0;
+        }
+        output.shrink()
+    }
+}
+
+impl PartialOrd for BigInt {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        let biggest_length = self.numbers.len().max(other.numbers.len());
+        for i in (0..biggest_length).rev() {
+            if i >= self.numbers.len() && other.numbers[i] != 0 {
+                return Some(Ordering::Less);
+            } else if i >= other.numbers.len() && self.numbers[i] != 0 {
+                return Some(Ordering::Greater);
+            } else if i >= self.numbers.len() || i >= other.numbers.len() {
+                continue;
+            } else if self.numbers[i] < other.numbers[i] {
+                return Some(Ordering::Less);
+            } else if self.numbers[i] > other.numbers[i] {
+                return Some(Ordering::Greater);
+            }
+        }
+        Some(Ordering::Equal)
+    }
+}
+
+impl PartialEq for BigInt {
+    fn eq(&self, other: &Self) -> bool {
+        self.partial_cmp(other) == Some(Ordering::Equal)
+    }
+}
+
+type Item = BigInt;
+
+#[derive(Clone)]
+struct Monkey {
+    index: usize,
+    items: Vec<Item>,
+    inspected_items: usize,
+    operation: Rc<dyn Fn(Item) -> Item>,
+    test_divisible_by: Item,
+    test_true: usize,
+    test_false: usize,
+}
+
+impl std::fmt::Debug for Monkey {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("Monkey")
+            .field("index", &self.index)
+            .field("items", &self.items)
+            .field("inspected_items", &self.inspected_items)
+            .field("test_divisible_by", &self.test_divisible_by)
+            .field("test_true", &self.test_true)
+            .field("test_false", &self.test_false)
+            .finish()
+    }
+}
+
+impl Monkey {
+    fn parse(input: &mut Lines) -> Option<Self> {
+        let mut input = input
+            .take_while(|line| !line.is_empty())
+            .map(|line| line.split_whitespace().collect::<Vec<_>>());
+        let index = match &input.next()?[..] {
+            ["Monkey", i] => i.replace(':', "").parse().unwrap(),
+            l => panic!("invalid line: {l:?}"),
+        };
+        let line = input.next()?;
+        let items = match &line[..2] {
+            ["Starting", "items:"] => line[2..]
+                .iter()
+                .map(|n| n.replace(',', "").parse::<u64>().unwrap().into())
+                .collect::<Vec<_>>(),
+            l => panic!("invalid line: {l:?}"),
+        };
+        let operation: Rc<dyn Fn(Item) -> Item> = match &input.next()?[..] {
+            ["Operation:", "new", "=", "old", "+", "old"] => Rc::new(|old| old.clone() + old),
+            ["Operation:", "new", "=", "old", "+", n] => {
+                let n: Item = n.parse::<u64>().unwrap().into();
+                Rc::new(move |old| old + n.clone())
+            }
+            ["Operation:", "new", "=", "old", "*", "old"] => Rc::new(|old| old.clone() * old),
+            ["Operation:", "new", "=", "old", "*", n] => {
+                let n: Item = n.parse::<u64>().unwrap().into();
+                Rc::new(move |old| old * n.clone())
+            }
+            l => panic!("invalid line: {l:?}"),
+        };
+        let test_divisible_by = match &input.next()?[..] {
+            ["Test:", "divisible", "by", n] => n.parse::<u64>().unwrap().into(),
+            l => panic!("invalid line: {l:?}"),
+        };
+        let test_true = match &input.next()?[..] {
+            ["If", "true:", "throw", "to", "monkey", n] => n.parse().unwrap(),
+            l => panic!("invalid line: {l:?}"),
+        };
+        let test_false = match &input.next()?[..] {
+            ["If", "false:", "throw", "to", "monkey", n] => n.parse().unwrap(),
+            l => panic!("invalid line: {l:?}"),
+        };
+        Some(Self {
+            index,
+            items,
+            operation,
+            test_divisible_by,
+            test_true,
+            test_false,
+            inspected_items: 0,
+        })
+    }
+
+    fn execute_round(
+        &mut self,
+        relief: impl Fn(Item) -> Item,
+    ) -> (usize, Vec<Item>, usize, Vec<Item>) {
+        let (items_true, items_false) = self
+            .items
+            .iter()
+            .map(|item| (self.operation)(item.clone()))
+            .map(relief)
+            .partition(|item| item.clone() % self.test_divisible_by.clone() == 0u64.into());
+        self.inspected_items += self.items.len();
+        self.items = vec![];
+        (self.test_true, items_true, self.test_false, items_false)
+    }
+}
+
+fn execute_round(monkeys: &mut [Monkey], relief: impl Fn(Item) -> Item) {
+    for index in 0..monkeys.len() {
+        let (index_true, mut items_true, index_false, mut items_false) =
+            monkeys[index].execute_round(&relief);
+        monkeys[index_true].items.append(&mut items_true);
+        monkeys[index_false].items.append(&mut items_false);
+    }
+}
+
+fn calc_monkey_business(monkeys: &[Monkey]) -> usize {
+    let mut inspected_items = monkeys
+        .iter()
+        .map(|monkey| monkey.inspected_items)
+        .collect::<Vec<_>>();
+    inspected_items.sort_by_key(|&items| Reverse(items));
+    inspected_items.iter().take(2).product()
+}
+
+fn main() {
+    let input = "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";
+    let input = read_to_string("input.txt").unwrap_or_else(|_| input.to_owned());
+    let mut lines = input.lines();
+    let mut monkeys = vec![];
+    while let Some(monkey) = Monkey::parse(&mut lines) {
+        lines.next();
+        monkeys.push(monkey);
+    }
+    let min_product: BigInt = monkeys
+        .iter()
+        .map(|monkey| monkey.test_divisible_by.clone())
+        .fold(1.into(), |p, i| p * i);
+    let mut monkeys2 = monkeys.clone();
+
+    for _ in 0..20 {
+        execute_round(&mut monkeys, |item| item / Item::from(3u64));
+    }
+
+    let monkey_business = calc_monkey_business(&monkeys);
+    println!("monkey business: {monkey_business}");
+
+    println!("starting 10000 iterations");
+    for i in 0..10_000 {
+        print!("executing round {i}\r");
+        std::io::stdout().flush().unwrap();
+        execute_round(&mut monkeys2, |item| item % min_product.clone());
+    }
+    let monkey_business = calc_monkey_business(&monkeys2);
+    println!("monkey business: {monkey_business}");
+}
+
+#[cfg(test)]
+mod tests {
+    use super::BigInt;
+    #[test]
+    fn big_int() {
+        let x: BigInt = 1.into();
+        let y: BigInt = 1.into();
+        assert_eq!(
+            x.clone() << 64,
+            BigInt {
+                numbers: vec![0, 1]
+            }
+        );
+        assert_eq!(
+            x.clone() << 2,
+            BigInt {
+                numbers: vec![0b100, 0]
+            }
+        );
+        assert_eq!(
+            x.clone() << 65,
+            BigInt {
+                numbers: vec![0, 2, 0]
+            }
+        );
+        assert_eq!(x.clone() + y.clone(), 2.into());
+        assert_eq!(x.clone() - y.clone(), 0.into());
+        assert_eq!(x.clone() * y.clone(), 1.into());
+        assert_eq!(x.clone() / y.clone(), 1.into());
+        assert_eq!(x % y, 0.into());
+
+        let x: BigInt = 101.into();
+        let y: BigInt = 10.into();
+        assert_eq!(x.clone() + y.clone(), 111.into());
+        assert_eq!(x.clone() - y.clone(), 91.into());
+        assert_eq!(x.clone() * y.clone(), 1010.into());
+        assert_eq!(x.clone() / y.clone(), 10.into());
+        assert_eq!(x % y, 1.into());
+    }
 }