# Dart Not very happy with this, as for part 2 the code just told me which four pairs of bits of the output needed investigation and I then tediously worked through how they differed from the correct adder implementation in the debugger. Spoilered as it is overly long and not very interesting. ::: spoiler spoiler ``` import 'package:collection/collection.dart'; import 'package:more/more.dart'; var nodes = {}; class Node { String name = ''; bool? state; var outputGates = []; } class Wire implements Node { @override String name; @override bool? state; @override var outputGates = []; Wire(this.name, this.state); set() { for (var g in outputGates) { (nodes[g]! as Gate).set(); } } } class Gate implements Node { String input1, input2, type; @override String name; @override bool? state; @override var outputGates = []; Gate(this.name, this.input1, this.input2, this.type); set() { var a = nodes[input1]!.state; var b = nodes[input2]!.state; if (a == null || b == null) return; state = switch (type) { 'AND' => a && b, 'OR' => a || b, _ => a ^ b }; for (var g in outputGates) { (nodes[g]! as Gate).set(); } } } void setup(List lines) { var parts = lines.splitAfter((e) => e.isEmpty); Map wires = Map.fromEntries(parts.first.skipLast(1).map((e) { var p = e.split(': '); return MapEntry(p[0], Wire(p[0], p[1] == '1')); })); nodes = Map.fromEntries(parts.last.map((e) { var p = e.split(' '); return MapEntry(p.last, Gate(p.last, p[0], p[2], p[1])); })); nodes.addAll(wires); for (var g in nodes.values) { if (g is! Gate) continue; nodes[g.input1]!.outputGates.add(g.name); nodes[g.input2]!.outputGates.add(g.name); } } String line(String s) => nodes.keys .where((e) => e.startsWith(s)) .sorted() .reversed .map((e) => nodes[e]!.state! ? '1' : '0') .join(''); part1(List lines) { setup(lines); nodes.values.whereType().forEach((e) => e.set()); return int.parse(line('z'), radix: 2); } part2(List lines) { setup(lines); var bits = nodes.keys.count((e) => e.startsWith('x')); for (var b in 0.to(bits)) { nodes.values.whereType().forEach((e) => e.state = null); nodes.values.whereType().forEach(((e) => e.state = false)); nodes['y${b.toString().padLeft(2, "0")}']!.state = true; nodes.values.whereType().forEach((e) => e.set()); print('${line("x")}\t${line("y")}\t${line("z")}\t$b'); var output = line('z'); for (var i in 0.to(bits)) { if (output[bits - i] != ((i == b) ? "1" : "0")) print(i); } } tree('z05'); tree('z06'); // Add break point here and inspect and solve manually using `tree`. print('break here'); } tree(String s, {indent = ''}) { var here = nodes[s]!; if (here is Wire) { print('$indent${here.name} (wire)'); return; } here as Gate; print('$indent${here.name} ${here.type}'); tree(here.input1, indent: indent + '| '); tree(here.input2, indent: indent + '| '); } ``` :::

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