159 lines
4.7 KiB
Rust
159 lines
4.7 KiB
Rust
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use std::num::ParseIntError;
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use std::env;
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use std::fs::File;
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use std::io::{self, BufRead, Lines};
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use std::collections::VecDeque;
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#[derive(Debug)]
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enum Operator { Add, Mul }
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#[derive(Debug)]
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enum Operand { Old, Imm(u64) }
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#[derive(Debug)]
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struct Operation { left: Operand, op: Operator, right: Operand }
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impl Operation {
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fn perform(&self, old: u64) -> u64 {
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let left = match self.left {
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Operand::Old => old,
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Operand::Imm(x) => x,
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};
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let right = match self.right {
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Operand::Old => old,
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Operand::Imm(x) => x,
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};
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match self.op {
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Operator::Add => left + right,
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Operator::Mul => left * right,
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}
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}
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}
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#[derive(Debug)]
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struct Monkey {
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id: u64,
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items: VecDeque<u64>,
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operation: Operation,
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div_by_test: u64,
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true_throw: u64,
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false_throw: u64,
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}
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#[derive(Debug)]
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enum MonkeyError {
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ParseError(),
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ParseIntError(ParseIntError),
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IoError(io::Error),
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}
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impl From<ParseIntError> for MonkeyError {
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fn from(e: ParseIntError) -> Self { MonkeyError::ParseIntError(e) }
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}
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impl From<io::Error> for MonkeyError {
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fn from(e: io::Error) -> Self { MonkeyError::IoError(e) }
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}
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fn parse_monkey<B: BufRead>(
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lines: &mut Lines<B>
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) -> Result<Option<Monkey>, MonkeyError> {
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let id = match lines.next() {
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Some(line) => line?
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.strip_prefix("Monkey ").ok_or(MonkeyError::ParseError())?
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.strip_suffix(":").ok_or(MonkeyError::ParseError())?
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.parse::<u64>()?,
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None => return Ok(None),
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};
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let starting_items = lines.next().ok_or(MonkeyError::ParseError())??
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.strip_prefix(" Starting items: ").ok_or(MonkeyError::ParseError())?
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.split(", ")
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.map(|item| item.parse::<u64>())
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.collect::<Result<VecDeque<_>, _>>()?;
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let op_line = lines.next().ok_or(MonkeyError::ParseError())??;
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let op_vec = op_line
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.strip_prefix(" Operation: new = ").ok_or(MonkeyError::ParseError())?
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.split(' ').collect::<Vec<_>>();
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let (left, operator, right) = (op_vec[0], op_vec[1], op_vec[2]);
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let operation = Operation {
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left: match left {
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"old" => Operand::Old,
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_ => Operand::Imm(left.parse()?)
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},
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op: match operator {
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"+" => Ok(Operator::Add),
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"*" => Ok(Operator::Mul),
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_ => Err(MonkeyError::ParseError())
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}?,
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right: match right {
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"old" => Operand::Old,
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_ => Operand::Imm(right.parse()?)
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},
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};
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let test_val = lines.next().ok_or(MonkeyError::ParseError())??
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.strip_prefix(" Test: divisible by ").ok_or(MonkeyError::ParseError())?
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.parse::<u64>()?;
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let true_throw = lines.next().ok_or(MonkeyError::ParseError())??
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.strip_prefix(" If true: throw to monkey ")
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.ok_or(MonkeyError::ParseError())?
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.parse::<u64>()?;
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let false_throw = lines.next().ok_or(MonkeyError::ParseError())??
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.strip_prefix(" If false: throw to monkey ")
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.ok_or(MonkeyError::ParseError())?
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.parse::<u64>()?;
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// Remove empty line if exists
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match lines.next() {
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None => Ok(()),
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Some(Err(e)) => Err(e),
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Some(Ok(s)) => Ok(match s.as_str() {
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"" => Ok(()),
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_ => Err(MonkeyError::ParseError()),
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}?),
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}?;
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Ok(Some(Monkey {
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id: id,
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items: starting_items,
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operation: operation,
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div_by_test: test_val,
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true_throw: true_throw,
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false_throw: false_throw,
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})
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)}
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fn main() {
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let file = File::open(&env::args().nth(1).unwrap()).unwrap();
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let mut lines = io::BufReader::new(file).lines();
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let mut monkeys: Vec<Monkey> = Vec::new();
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loop {
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match parse_monkey(&mut lines) {
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Ok(None) => break,
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Ok(Some(m)) => { assert!(m.id == monkeys.len() as u64); monkeys.push(m) },
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Err(e) => eprintln!("{:?}", e),
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}
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}
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let mut monkey_item_counts = vec![0; monkeys.len()];
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for _round in 1..=20 {
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for i in 0..monkeys.len() {
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monkey_item_counts[i] += monkeys[i].items.len();
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for _item in 0..monkeys[i].items.len() {
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let old_item = monkeys[i].items.pop_front().unwrap();
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let new_item = monkeys[i].operation.perform(old_item) / 3;
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let new_i = if new_item % monkeys[i].div_by_test == 0 {
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monkeys[i].true_throw
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} else {
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monkeys[i].false_throw
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} as usize;
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monkeys[new_i].items.push_back(new_item);
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}
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}
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}
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monkey_item_counts.sort_by(|x, y| y.cmp(x));
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println!("{:?}", monkey_item_counts[0]*monkey_item_counts[1]);
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}
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