Advent Of Code 2020 Day 1 in dart

aoc2020_1.dart

void main() {
  int i = 0;
  final List<AdventSolution> solutions = [
    AdventSolution1(inputAdvent1),
    AdventSolution2(inputAdvent1)
  ];
  solutions.forEach((s) => print("Advent ${++i} solution: ${s.solution}"));
}

// Full inputs at https://adventofcode.com/2020/day/1/input
const inputAdvent1 = """1721
979
366
299
675
1456""";

abstract class AdventSolution {
  final List<int> expenses;
  AdventSolution(String inputs) : expenses = AdventSolution.parseInputs(inputs);

  static List<int> parseInputs(String inputs) => inputs
      .split("\n")
      .where((element) => element.isNotEmpty)
      .map((element) => int.parse(element))
      .toList();

  String get solution => _getSolution();

  String _getSolution();
}

class AdventSolution1 extends AdventSolution {
  AdventSolution1(inputs) : super(inputs);

  String _getSolution() {
    var product;
    for (var expense in expenses) {
      var index = expenses.indexWhere(
          (element) => element != expense && element + expense == 2020);
      if (index == -1) {
        continue;
      }
      product = expenses[index] * expense;
    }
    return product?.toString();
  }
}

class AdventSolution2 extends AdventSolution {
  AdventSolution2(inputs) : super(inputs);

  String _getSolution() {
    int product;
    for (var eA in expenses) {
      for (var eB in expenses) {
        if (eB == eA) {
          continue;
        }
        for (var eC in expenses) {
          if (eC == eA || eC == eB) {
            continue;
          }
          if ((eA + eB + eC) == 2020) {
            product = eA * eB * eC;
            break;
          }
        }
        if (product != null) {
          break;
        }
      }
      if (product != null) {
        break;
      }
    }

    return product.toString();
  }
}