Advent Of Code 2020 Day 10 in dart

aoc2020_10.dart

import 'dart:math';

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

// Full inputs at https://adventofcode.com/2020/day/10/input
const inputsDay10 = """28
33
18
42
31
14
46
20
48
47
24
23
49
45
19
38
39
11
1
32
25
35
8
17
7
9
4
2
34
10
3""";

List<int> _parseInputs(String inputs) => inputs
    .split('\n')
    .where((el) => el.isNotEmpty)
    .map((e) => int.parse(e))
    .toList();
List<int> _inputs = _parseInputs(inputsDay10b);

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

  // implement in subclass
  String getSolution();

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

abstract class _Day10Solution extends AdventSolution {
  _Day10Solution(name) : super(10, name);
}

class SolutionA extends _Day10Solution {
  SolutionA() : super('A');

  String getSolution() {
    _inputs.sort();
    var jolt = 0, diff1 = 0, diff2 = 0, diff3 = 1;
    for (var num in _inputs) {
      var diff = num - jolt;
      if (diff > 3) {
        throw "Joltage rating exceeded";
      }
      jolt = num;
      switch (diff) {
        case 1:
          diff1++;
          break;
        case 2:
          diff2++;
          break;
        case 3:
          diff3++;
          break;
      }
    }
    return (diff1 * diff3).toString();
  }
}

class SolutionB extends _Day10Solution {
  SolutionB() : super('B');

  String getSolution() {
    var jolt = 0, diffs = '';
    for (var num in _inputs) {
      var diff = num - jolt;
      if (diff > 3) {
        throw "Joltage rating exceeded";
      }
      jolt = num;
      diffs += diff.toString();
    }
    diffs += '3';

    // get sequences of 2, 3, or 4 1-diff jolts in a row
    var seq = diffs.split('3'),
        // get count of each seq
        diff2 = seq.fold(0, (prev, el) => el == '11' ? ++prev : prev),
        diff3 = seq.fold(0, (prev, el) => el == '111' ? ++prev : prev),
        diff4 = seq.fold(0, (prev, el) => el == '1111' ? ++prev : prev);

    // get total by multiplying total number of permutations of each seq option
    return ((diff2 > 0 ? pow(2, diff2) : 1) * // diff2 = 2 permutations
            (diff3 > 0 ? pow(4, diff3) : 1) * // diff3 = 4 permutations
            (diff4 > 0 ? pow(7, diff4) : 1)) // diff4 = 7 permutations
        .toString();
  }
}