kageru/advent-of-code
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2020/18/2

This commit is contained in:
kageru 2020-12-18 11:44:45 +01:00
parent d313bd6e25
commit 5c87450e11
1 changed files with 58 additions and 36 deletions
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94
2020/src/bin/day18.rs
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@ -2,6 +2,7 @@
extern crate test;
use aoc2020::common::*;
use itertools::Itertools;
use std::collections::VecDeque;
type Parsed = Vec<Vec<Operation>>;
@ -36,39 +37,16 @@ fn parse_input(raw: &str) -> Parsed {
}
fn part1(parsed: &Parsed) -> usize {
parsed.iter().map(|l| p1_rec(l)).sum()
parsed.iter().map(|l| build_stack(l, execute_stack_p1)).sum()
}
fn p1_rec(ops: &[Operation]) -> usize {
// dbg!(ops);
let mut stack = vec![];
let mut parens = 0;
for i in 0..ops.len() {
match ops[i] {
Operation::OpenParen if parens > 0 => {
parens += 1;
}
Operation::CloseParen if parens > 0 => {
parens -= 1;
}
_ if parens > 0 => continue,
Operation::Add => stack.push(ops[i]),
Operation::Multiply => stack.push(ops[i]),
Operation::Number(n) => stack.push(Operation::Number(n)),
Operation::OpenParen => {
stack.push(Operation::Number(p1_rec(&ops[i + 1..])));
parens += 1;
}
Operation::CloseParen => break,
}
while stack.len() > 2 {
let drained = stack.drain(..3).collect_vec();
// dbg!(&drained, parens);
match drained[..] {
[Operation::Number(x), Operation::Add, Operation::Number(y)] => stack.push(Operation::Number(x + y)),
[Operation::Number(x), Operation::Multiply, Operation::Number(y)] => stack.push(Operation::Number(x * y)),
_ => unreachable!("Invalid stack: {:?} of size {}", drained, drained.len()),
}
fn execute_stack_p1(mut stack: VecDeque<Operation>) -> usize {
while stack.len() > 2 {
let drained = stack.drain(..3).collect_vec();
match drained[..] {
[Operation::Number(x), Operation::Add, Operation::Number(y)] => stack.push_front(Operation::Number(x + y)),
[Operation::Number(x), Operation::Multiply, Operation::Number(y)] => stack.push_front(Operation::Number(x * y)),
_ => unreachable!("Invalid stack: {:?}", drained),
}
}
if let Operation::Number(n) = stack[0] {
@ -78,8 +56,52 @@ fn p1_rec(ops: &[Operation]) -> usize {
}
}
fn execute_stack_p2(mut stack: VecDeque<Operation>) -> usize {
while let Some(i) = stack.iter().position(|o| o == &Operation::Add) {
let drained = stack.drain(i - 1..=i + 1).collect_vec();
match drained[..] {
[Operation::Number(x), Operation::Add, Operation::Number(y)] => stack.insert(i - 1, Operation::Number(x + y)),
_ => unreachable!("Invalid stack: {:?}", drained),
}
}
while stack.len() > 2 {
let drained = stack.drain(..3).collect_vec();
match drained[..] {
[Operation::Number(x), Operation::Multiply, Operation::Number(y)] => stack.push_front(Operation::Number(x * y)),
_ => unreachable!("Invalid stack: {:?}", drained),
}
}
if let Operation::Number(n) = stack[0] {
n
} else {
unreachable!()
}
}
fn build_stack<F: FnOnce(VecDeque<Operation>) -> usize + Copy>(ops: &[Operation], execute_stack: F) -> usize {
let mut stack = VecDeque::new();
let mut parens = 0;
for i in 0..ops.len() {
match ops[i] {
Operation::OpenParen if parens > 0 => parens += 1,
#[rustfmt::skip]
Operation::CloseParen => if parens > 0 { parens -= 1 } else { break },
// skip the entries that one of the recursive children is already processing
_ if parens > 0 => continue,
Operation::Add => stack.push_back(ops[i]),
Operation::Multiply => stack.push_back(ops[i]),
Operation::Number(n) => stack.push_back(Operation::Number(n)),
Operation::OpenParen => {
stack.push_back(Operation::Number(build_stack(&ops[i + 1..], execute_stack)));
parens += 1;
}
}
}
execute_stack(stack)
}
fn part2(parsed: &Parsed) -> usize {
unimplemented!()
parsed.iter().map(|l| build_stack(l, execute_stack_p2)).sum()
}
fn main() {
@ -98,8 +120,8 @@ mod tests {
const TEST_INPUT: &str = "((2 + 4 * 9) * (6 + 9 * 8 + 6) + 6) + 2 + 4 * 2";
test!(part1() == 13632);
//test!(part2() == 0);
//bench!(part1() == 0);
//bench!(part2() == 0);
//bench_input!(len == 0);
test!(part2() == 23340);
bench!(part1() == 510009915468);
bench!(part2() == 321176691637769);
bench_input!(len == 375);
}