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|
static DAY: u8 = 11;
fn main() {
let input = advent::read_lines(DAY);
println!("{DAY}a: {}", monkey_business(&input, 20, false));
println!("{DAY}b: {}", monkey_business(&input, 10000, true));
}
#[derive(Debug, Clone)]
enum Operation {
Add { operand: Option<usize> },
Mul { operand: Option<usize> },
}
impl Operation {
fn new(input: &str) -> Operation {
let fixed = " Operation: new = old ";
let mut it = input.chars().skip(fixed.len());
let operation = it.next().unwrap();
it.next(); // space
let operand = it.collect::<String>();
let operand = operand.parse::<usize>().ok();
match operation {
'+' => Operation::Add { operand },
'*' => Operation::Mul { operand },
_ => unimplemented!(),
}
}
fn compute(&self, old: usize) -> usize {
match *self {
Operation::Add { operand: None } => old + old,
Operation::Add { operand: Some(operand) } => old + operand,
Operation::Mul { operand: None } => old * old,
Operation::Mul { operand: Some(operand) } => old * operand,
}
}
}
#[derive(Debug, Clone)]
struct Test {
divisible: usize,
iftrue: usize,
iffalse: usize,
}
impl Test {
fn new(input: &[String]) -> Test {
let fixed1 = " Test: divisible by ";
let divisible = input[0].chars()
.skip(fixed1.len())
.collect::<String>()
.parse().unwrap();
let fixed2 = " If true: throw to monkey ";
let iftrue = input[1].chars()
.nth(fixed2.len()).unwrap()
.to_digit(10).unwrap() as usize;
let iffalse = input[2].chars()
.nth(fixed2.len() + 1).unwrap()
.to_digit(10).unwrap() as usize;
Test { divisible, iftrue, iffalse }
}
fn eval(&self, operand: usize) -> usize {
if operand % self.divisible == 0 {
self.iftrue
} else {
self.iffalse
}
}
}
#[derive(Debug, Clone)]
struct Monkey {
items: Vec<usize>,
operation: Operation,
test: Test,
inspections: usize,
}
impl Monkey {
fn new(input: &[String]) -> Monkey {
/*let id = input[0].chars()
.skip(7)
.next().unwrap()
.to_digit(10).unwrap();*/
let items = input[1].split_once(':').unwrap().1
.split(',')
.map(|x| x.trim().parse().unwrap())
.collect();
let operation = Operation::new(&input[2]);
let test = Test::new(&input[3..]);
Monkey { items, operation, test, inspections: 0 }
}
}
fn monkey_business(input: &[String], rounds: usize, worried: bool) -> usize {
let mut monkeys = Vec::new();
for lines in input.chunks(7) {
let monkey = Monkey::new(lines);
monkeys.push(monkey);
}
let divisibility : usize = monkeys.iter()
.map(|m| m.test.divisible)
.product();
for _ in 0 .. rounds {
for i in 0 .. monkeys.len() {
for item in monkeys[i].items.clone() {
monkeys[i].inspections += 1;
let mut worry = monkeys[i].operation.compute(item);
if !worried {
worry /= 3;
} else {
/* all divisibility tests are prime, so it's possible
to reduce the worry level by the product of all values */
worry %= divisibility;
}
let next = monkeys[i].test.eval(worry);
monkeys[next].items.push(worry);
}
monkeys[i].items.clear();
}
}
let mut inspections = monkeys.iter()
.map(|m| m.inspections)
.collect::<Vec<_>>();
inspections.sort();
inspections.iter()
.rev()
.take(2)
.product()
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
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",
].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
assert_eq!(monkey_business(&input, 20, false), 10605);
assert_eq!(monkey_business(&input, 10000, true), 2713310158);
}
}
|
