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day_11.rs
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day_11.rs
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use std::collections::VecDeque;
use common::{Answer, Solution};
pub struct Day11;
impl Solution for Day11 {
fn name(&self) -> &'static str {
"Monkey in the Middle"
}
fn part_a(&self, input: &str) -> Answer {
let monkeys = parse_monkeys(input);
process(monkeys, 20, |x| x / 3).into()
}
fn part_b(&self, input: &str) -> Answer {
let monkeys = parse_monkeys(input);
let magic = monkeys.iter().map(|x| x.test.divisor).product::<u64>();
process(monkeys, 10000, |x| x % magic).into()
}
}
struct Monkey {
items: VecDeque<u64>,
inspected: usize,
operation: Operation,
test: Test,
}
enum Operation {
Add(u64),
Multiply(u64),
Square,
}
struct Test {
divisor: u64,
// [true, false]
monkey: [usize; 2],
}
fn process(mut monkeys: Vec<Monkey>, iter: usize, proc: impl Fn(u64) -> u64) -> usize {
for _ in 0..iter {
for m in 0..monkeys.len() {
while let Some(item) = monkeys[m].items.pop_front() {
monkeys[m].inspected += 1;
let item = proc(monkeys[m].operation.process(item));
let goto = monkeys[m].test.process(item);
monkeys[goto].items.push_back(item);
}
}
}
monkeys.sort_unstable_by_key(|x| x.inspected);
monkeys.pop().unwrap().inspected * monkeys.pop().unwrap().inspected
}
fn parse_monkeys(raw: &str) -> Vec<Monkey> {
let mut out = Vec::new();
for i in raw.lines().collect::<Vec<_>>().chunks(7) {
let items = i[1]
.split_once(": ")
.unwrap()
.1
.split(", ")
.map(|x| x.parse::<u64>().unwrap())
.collect::<VecDeque<_>>();
let operation = Operation::parse(i[2].split_once(" = ").unwrap().1);
let test = Test::parse(&i[3..6]);
out.push(Monkey {
items,
inspected: 0,
operation,
test,
});
}
out
}
impl Operation {
fn parse(inp: &str) -> Self {
let mut parts = inp.split_whitespace();
assert_eq!(parts.next().unwrap(), "old");
let op = parts.next().unwrap();
let value = parts.next().unwrap();
match op {
"*" => match value {
"old" => Self::Square,
_ => Self::Multiply(value.parse::<u64>().unwrap()),
},
"+" => Self::Add(value.parse::<u64>().unwrap()),
_ => panic!("Unsuppored operation"),
}
}
fn process(&self, old: u64) -> u64 {
match self {
Self::Add(x) => old + x,
Self::Multiply(x) => old * x,
Self::Square => old * old,
}
}
}
impl Test {
fn parse(inp: &[&str]) -> Self {
let divisor = inp[0].split_once("by ").unwrap().1.parse::<u64>().unwrap();
let mut monkey = [0; 2];
for (i, line) in inp[1..].iter().enumerate() {
let monkey_id = line
.split_once("monkey ")
.unwrap()
.1
.parse::<usize>()
.unwrap();
monkey[i] = monkey_id;
}
Self { divisor, monkey }
}
fn process(&self, item: u64) -> usize {
if item % self.divisor == 0 {
return self.monkey[0];
}
self.monkey[1]
}
}