AOC2020/aoc2020/lib/aoc20201203.dart

import 'package:aoc2020/aocbase.dart';
import 'package:aoc2020/model/point.dart';
import 'package:aoc2020/model/readdata.dart';

class AOC20201203 extends AOCBase {
  static const tree = '#';

  int indexWrap({int index, int width}) => index % width;

  int treeTest({int index, String line}) {
    var testChar = line[indexWrap(index: index, width: line.length)];
    return testChar == tree ? 1 : 0;
  }

  int tobogganRide({List<String> hill, Point start, Point slope}) {
    var numberOfTrees = 0;
    var pos = start;
    for (var lineNum = 0; lineNum < hill.length; lineNum += slope.item2) {
      numberOfTrees += treeTest(index: pos.item1, line: hill[lineNum]);
      pos = pos + slope;
    }
    return numberOfTrees;
  }

  @override
  Future<void> a({bool test}) async {
    var mylist = await ReadData.readFile<String>(classString, test: test);
    answerA = tobogganRide(hill: mylist, start: Point(0, 0), slope: Point(3, 1));
  }

  @override
  Future<void> b({bool test}) async {
    var mylist = await ReadData.readFile<String>(classString, test: test);

    var slopes = <Point>[Point(1, 1), Point(3, 1), Point(5, 1), Point(7, 1), Point(1, 2)];
    answerB = 0;
    for (var slope in slopes) {
      var trees = tobogganRide(hill: mylist, start: Point(0, 0), slope: slope);
      answerB = (answerB == 0) ? trees : answerB * trees;
    }
  }
}