AoC 2022 day 9 - dart original code

acc_2022_day_9.dart

import 'dart:io';

void main(List<String> args) async {
  final input = File('day9.input')
      .readAsStringSync()
      .split('\n')
      .map((e) => e.split(' '))
      .map((e) => [e[0], int.parse(e[1])]);

  int offset = 100000;
  int hx = offset;
  int hy = offset;
  List<List<int>> tails = List.generate(9, (index) => [offset, offset]);
  List<Set<int>> visited = List.generate(9, (index) => {});
  addAll(tails, visited, offset);

  input.forEach((element) {
    int steps = element[1] as int;
    switch (element[0]) {
      case 'R':
        for (int i = 0; i < steps; i++) {
          hx++;
          updateTails(tails, hx, hy);
          addAll(tails, visited, offset);
          print('R');
        }
        break;
      case 'L':
        for (int i = 0; i < steps; i++) {
          hx--;
          updateTails(tails, hx, hy);
          addAll(tails, visited, offset);
          print('L');
        }
        break;
      case 'D':
        for (int i = 0; i < steps; i++) {
          hy--;
          updateTails(tails, hx, hy);
          addAll(tails, visited, offset);
          print('D');
        }

        break;
      case 'U':
        for (int i = 0; i < steps; i++) {
          hy++;
          updateTails(tails, hx, hy);
          addAll(tails, visited, offset);
          print('U');
        }
        break;
    }
  });

  print(visited.first.length);
  print(visited.last.length);
}

void updateTails(List<List<int>> tails, int hx, int hy) {
  tails.insert(0, updateTail(tails.removeAt(0), hx, hy));
  for (int i = 1; i < tails.length; i++) {
    List<int> head = tails[i - 1];
    List<int> tail = tails.removeAt(i);
    tails.insert(i, updateTail(tail, head[0], head[1]));
  }
}

void addAll(List<List<int>> tails, List<Set<int>> visited, int s) {
  for (int i = 0; i < tails.length; i++) {
    visited[i].add(tails[i][0] * s + tails[i][1]);
  }
}

List<int> updateTail(List<int> tail, int hx, int hy) {
  int tx = tail[0];
  int ty = tail[1];

  int dx = hx - tx;
  int dy = hy - ty;
  switch (dx) {
    case 2:
      {
        switch (dy) {
          case 0:
            print(' t R');
            return [tx + 1, ty];
          case -1:
            print(' t RD');
            return [tx + 1, ty - 1];
          case 1:
            print(' t RU');
            return [tx + 1, ty + 1];
          case 2:
            print(' ! RU');
            return [tx + 1, ty + 1];
          case -2:
            print(' ! RD');
            return [tx + 1, ty - 1];
        }
        break;
      }
    case 1:
      {
        switch (dy) {
          case 0:
          case 1:
          case -1:
            return [tx, ty];
          case 2:
            print(' t UR');
            return [tx + 1, ty + 1];
          case -2:
            print(' t DR');
            return [tx + 1, ty - 1];
        }
        break;
      }
    case 0:
      {
        switch (dy) {
          case 0:
          case 1:
          case -1:
            return [tx, ty];
          case 2:
            print(' t U');
            return [tx, ty + 1];
          case -2:
            print(' t D');
            return [tx, ty - 1];
        }
        break;
      }
    case -1:
      {
        switch (dy) {
          case 0:
          case 1:
          case -1:
            return [tx, ty];
          case 2:
            print(' t LU');
            return [tx - 1, ty + 1];
          case -2:
            print(' t LD');
            return [tx - 1, ty - 1];
        }
        break;
      }
    case -2:
      {
        switch (dy) {
          case -1:
            print(' t LD');
            return [tx - 1, ty - 1];
          case 0:
            print(' t L');
            return [tx - 1, ty];
          case 1:
            print(' t LU');
            return [tx - 1, ty + 1];
          case 2:
            print(' ! LU');
            return [tx - 1, ty + 1];
          case -2:
            print(' ! LD');
            return [tx - 1, ty - 1];
        }
        break;
      }
  }
  print(' Not yet implemented case: $dx $dy');
  throw ArgumentError();
}