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start part 2
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1 changed files with 258 additions and 2 deletions
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@ -1,4 +1,4 @@
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use std::collections::HashMap;
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use std::collections::{HashMap, HashSet};
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use helper::{Day, IteratorExt, Variants};
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@ -121,7 +121,263 @@ fn part1(input: &str) -> u64 {
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result
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}
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fn part2(_input: &str) -> u64 {
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fn part2(input: &str) -> u64 {
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/*
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Adding two binary numbers
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LSB:
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X Y
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---|---|---
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| |
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+---|--+
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(^)--+ |
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| (&)-+
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| |
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---|---|---
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Z Carry
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other bits:
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X Y Carry
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---|---|---|---
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| | |
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| +---|-----+
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+---|---|--+ |
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| | | | |
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(^)--+ | +-(&)
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| | |
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+---(&)-+ |
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| | | |
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(^)------+ |
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| | |
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| (|)-------+
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| ++
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---|---|---
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Z Carry
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*/
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#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
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enum Wire<'a> {
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X(u8),
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Y(u8),
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Z(u8),
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Intermediate(&'a str),
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}
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#[derive(Debug, Clone, Copy)]
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enum Value {
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Unknown,
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Op(Op, usize, usize),
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}
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#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
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enum Op {
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And,
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Or,
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Xor,
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}
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let mut wires = Vec::new();
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let mut wire_names = Vec::new();
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let mut wire_by_name = HashMap::new();
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fn intern<'i>(
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wires: &mut Vec<Value>,
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wire_names: &mut Vec<Wire<'i>>,
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wire_by_name: &mut HashMap<Wire<'i>, usize>,
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name: &'i str,
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) -> (usize, Wire<'i>) {
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let name = if let Some(n) = name.strip_prefix("x") {
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Wire::X(n.parse().unwrap())
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} else if let Some(n) = name.strip_prefix("y") {
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Wire::Y(n.parse().unwrap())
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} else if let Some(n) = name.strip_prefix("z") {
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Wire::Z(n.parse().unwrap())
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} else {
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Wire::Intermediate(name)
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};
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let idx = *wire_by_name.entry(name).or_insert_with(|| {
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let idx = wires.len();
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wires.push(Value::Unknown);
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wire_names.push(name);
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idx
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});
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(idx, name)
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}
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let (_, gates) = input.split_once("\n\n").unwrap();
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let mut zs = Vec::new();
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for computed in gates.lines() {
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let (expr, wire) = computed.split_once(" -> ").unwrap();
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let [lhs, op, rhs] = expr.split(' ').collect_array().unwrap();
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let (wire, wire_name) = intern(&mut wires, &mut wire_names, &mut wire_by_name, wire);
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let (lhs, _) = intern(&mut wires, &mut wire_names, &mut wire_by_name, lhs);
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let (rhs, _) = intern(&mut wires, &mut wire_names, &mut wire_by_name, rhs);
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if let Wire::Z(_) = wire_name {
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zs.push(wire)
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}
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let op = match op {
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"AND" => Op::And,
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"OR" => Op::Or,
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"XOR" => Op::Xor,
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_ => panic!("Invalid op: {op}"),
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};
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wires[wire] = Value::Op(op, lhs, rhs);
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}
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zs.sort_by_key(|wire| wire_names[*wire]);
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#[derive(Debug, Clone, PartialEq, Eq, Hash)]
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enum Pattern {
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Op(Op, Box<Pattern>, Box<Pattern>),
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X(u8),
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Y(u8),
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}
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fn check_match(
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wire_names: &[Wire<'_>],
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wires: &[Value],
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check_cache: &mut HashMap<(usize, Pattern), Result<(), (usize, Pattern)>>,
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wire: usize,
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pattern: &Pattern,
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) -> Result<(), (usize, Pattern)> {
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let key = (wire, pattern.clone());
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if let Some(cache_value) = check_cache.get(&key) {
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return cache_value.clone();
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}
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let value = check_match_uncached(wire_names, wires, check_cache, wire, pattern);
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let prev_cache_entry = check_cache.insert(key, value.clone());
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assert!(prev_cache_entry.is_none());
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value
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}
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fn check_match_uncached(
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wire_names: &[Wire<'_>],
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wires: &[Value],
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check_cache: &mut HashMap<(usize, Pattern), Result<(), (usize, Pattern)>>,
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wire: usize,
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pattern: &Pattern,
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) -> Result<(), (usize, Pattern)> {
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//eprintln!("{:?} matches {:?}", wire_names[wire], pattern);
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match (wire_names[wire], pattern) {
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(_, Pattern::Op(_, _, _)) => {}
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(Wire::X(x_value), Pattern::X(x_pattern)) if x_value == *x_pattern => return Ok(()),
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(Wire::Y(y_value), Pattern::Y(y_pattern)) if y_value == *y_pattern => return Ok(()),
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_ => {
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return Err((wire, pattern.clone()));
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}
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}
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match (wires[wire], pattern) {
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(
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Value::Op(op_value, lhs_wire, rhs_wire),
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Pattern::Op(op_pattern, pattern1, pattern2),
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) if op_value == *op_pattern => {
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let lhs_1 = check_match(wire_names, wires, check_cache, lhs_wire, &pattern1);
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let rhs_2 = check_match(wire_names, wires, check_cache, rhs_wire, &pattern2);
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if lhs_1.is_ok() && rhs_2.is_ok() {
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return Ok(());
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}
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let lhs_2 = check_match(wire_names, wires, check_cache, lhs_wire, &pattern2);
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let rhs_1 = check_match(wire_names, wires, check_cache, rhs_wire, &pattern1);
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if lhs_2.is_ok() && rhs_1.is_ok() {
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return Ok(());
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}
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// If both inputs are wrong, this node is likely the culprit.
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// If only one input is wrong, this input is the culprit.
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if lhs_1.is_ok() {
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rhs_2
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} else if rhs_2.is_ok() {
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lhs_1
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} else if lhs_2.is_ok() {
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rhs_1
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} else if rhs_1.is_ok() {
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lhs_2
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} else {
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Err((wire, pattern.clone()))
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}
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}
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_ => Err((wire, pattern.clone())),
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}
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}
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let mut incorrect_gates = HashSet::new();
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let mut prev_carry_pat = Pattern::X(255); // dummy
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let mut check_cache = HashMap::new();
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for z_wire in zs {
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let Wire::Z(pos) = wire_names[z_wire] else {
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unreachable!()
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};
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eprintln!("------------ checking z{pos:0>2}");
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let input_xor_pat = Pattern::Op(
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Op::Xor,
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Box::new(Pattern::X(pos)),
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Box::new(Pattern::Y(pos)),
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);
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let (z_pat, carry_pat) = match pos {
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0 => {
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let carry_pat = Pattern::Op(
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Op::And,
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Box::new(Pattern::X(pos)),
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Box::new(Pattern::Y(pos)),
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);
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(input_xor_pat, carry_pat)
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}
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_ => {
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let carry_pat = Pattern::Op(
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Op::Or,
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Box::new(Pattern::Op(
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Op::And,
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Box::new(Pattern::X(pos)),
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Box::new(Pattern::Y(pos)),
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)),
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Box::new(Pattern::Op(
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Op::And,
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Box::new(prev_carry_pat.clone()),
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Box::new(input_xor_pat.clone()),
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)),
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);
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(
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Pattern::Op(Op::Xor, Box::new(input_xor_pat), Box::new(prev_carry_pat)),
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carry_pat,
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)
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}
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};
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prev_carry_pat = carry_pat;
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if let Err((incorrect_wire, pat)) =
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check_match(&wire_names, &wires, &mut check_cache, z_wire, &z_pat)
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{
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eprintln!("error: {:?}", wire_names[incorrect_wire]);
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incorrect_gates.insert((incorrect_wire, pat));
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}
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}
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dbg!(incorrect_gates.len());
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for (wire, pat) in &incorrect_gates {
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eprintln!("{:?}", wire_names[*wire]);
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let pair = incorrect_gates.iter().find(|(other_wire, other_pat)| {
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check_match(&wire_names, &wires, &mut check_cache, *wire, other_pat).is_ok()
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});
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if let Some(pair) = pair {
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eprintln!(" pairs with {:?}", wire_names[pair.0]);
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}
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}
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0
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}
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