AOC 2022 Day 10

/// A register gets updated by simple instructions
/// 1) What is its value at certain times?
/// 2) Draw a screen based on these. What letters can you see?

import 'package:more/more.dart';
import 'package:collection/collection.dart';

List<int> processRegisters(List<String> lines) {
  var screen = [1];
  parseInstr(String s) {
    screen.add(screen.last);
    if (s.startsWith('noop')) return;
    var n = int.parse(s.split(' ').last);
    screen.add(screen.last + n);
  }

  lines.forEach(parseInstr);
  return screen;
}

part1(List<String> lines) {
  var sig = processRegisters(lines);
  return [for (var i = 20; i < sig.length; i += 40) i * sig[i - 1]].sum;
}

part2(List<String> lines) {
  var sig = processRegisters(lines);
  var scr = List.filled(240, false);
  for (var i in 0.to(sig.length)) {
    scr[i % scr.length] |= (sig[i] - (i % 40)).abs() <= 1;
  }
  for (var i in 0.to(scr.length, step: 40)) {
    print(scr.sublist(i, i + 40).map((e) => e ? '#' : '.').join(''));
  }
  return readLetters(scr);
}

// Parse an AoC output to find the letters encoded in it.
readLetters(List<bool> l) {
  var hexes = l
      .chunked(5)
      .map((e) => e.take(4))
      .map((e) => int.parse(e.map((e) => e ? '1' : '0').join(''), radix: 2)
          .toRadixString(16))
      .toList();
  var ll = hexes.length ~/ 6;
  hex(x) => 0.to(hexes.length, step: ll).map((e) => hexes[x + e]).join('');
  return 0.to(ll).map((e) => letters[hex(e)] ?? '?').join('');
}

var letters = {
  '699e99': 'A',
  'e9e99e': 'B',
  '698896': 'C',
  'f8e88f': 'E',
  'f8e888': 'F',
  '698b97': 'G',
  '99f999': 'H',
  '311196': 'J',
  '88888f': 'L',
  'e99e88': 'P',
  'e99ea9': 'R',
  '999996': 'U',
  'f1248f': 'Z',
};