Advent Of Code 2020 Day 3 in dart

aoc2020_3.dart

void main() {
  final List<Object> solutions = [
    SolutionA(),
    SolutionB()
  ];
  solutions.forEach((s) => print(s.toString()));
}

// Full inputs at https://adventofcode.com/2020/day/3/input
var inputAdvent3 = """..##.......
#...#...#..
.#....#..#.
..#.#...#.#
.#...##..#.
..#.##.....
.#.#.#....#
.#........#
#.##...#...
#...##....#
.#..#...#.#""";

// get plot line objects from input string
List<PlotLine> _parseInputLines(String inputLines) => inputLines
    .split("\n")
    .where((element) => element.isNotEmpty)
    .map<PlotLine>((l) => PlotLine.fromString(l))
    .toList();
var _plotLines = _parseInputLines(inputAdvent3);

// convert string to List<SpaceType>
const _charOpen = ".";
const _charTree = "#";
enum SpaceType { open, tree }
List<SpaceType> _parseInputLine(String inputLine) => inputLine.runes
    .map<SpaceType>((f) =>
        String.fromCharCode(f) == _charTree ? SpaceType.tree : SpaceType.open)
    .toList();

// get total space type occurences at slope
int getCount(int rateX, int rateY, [SpaceType searchType = SpaceType.tree]) {
  var x = 0, y = 0, count = 0;
  do {
    x += rateX;
    y += rateY;
    if (y < _plotLines.length) {
      SpaceType type = _plotLines[y].spaceAt(x);
      if (type == searchType) {
        count++;
      }
    }
  } while (y < _plotLines.length);
  return count;
}

class PlotLine {
  final List<SpaceType> _template;
  PlotLine(List<SpaceType> inputLine) : _template = inputLine;
  PlotLine.fromString(String inputLine)
      : _template = _parseInputLine(inputLine);

  // get space type at x-index
  SpaceType spaceAt(int index) => _template[index % _template.length];
  String charAt(int index) =>
      spaceAt(index) == SpaceType.tree ? _charTree : _charOpen;
}

abstract class AdventSolution {
  final int day;
  final String name;
  AdventSolution(this.day, this.name);

  String get solution => getSolution();

  // implement in subclass
  String getSolution();

  @override
  String toString() {
    return "Advent Of Code, "
        "Day $day "
        "${name.isNotEmpty ? name : ''} "
        "solution: $solution";
  }
}


abstract class _Day3Solution extends AdventSolution {
  _Day3Solution(name) : super(3, name);
}


class SolutionA extends _Day3Solution {
  SolutionA() : super("A");

  String getSolution() {
    return getCount(3, 1).toString();
  }
}

class SolutionB extends _Day3Solution {
  SolutionB() : super("B");

  String getSolution() {
    var slopes = [
      [1, 1],
      [3, 1],
      [5, 1],
      [7, 1],
      [1, 2]
    ];
    return slopes
        .map<int>((s) => getCount(s[0], s[1]))
        .toList()
        .reduce((value, element) => element * value)
        .toString();
  }
}