AOC2020/aoc2020/lib/aoc20201209.dart

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

class AOC20201209 extends AOCBase {
  int testpreamble = 5;
  int runpreamble = 25;
  int preamble;
  int index;
  var mylist = <num>[];

  void init(String filename, bool test) async {
    mylist = await ReadData.readFileNum(filename);
    preamble = test ?? false ? testpreamble : runpreamble;
    index = preamble;
  }

  bool testGroup(int index) {
    var val = mylist[index];
    var sublist = Set.from(mylist.sublist(index - preamble, index));
    var testset = Set.from(sublist.map((elem) => val - elem));
    return testset.intersection(sublist).isNotEmpty;
  }

  List<num> sumTest(num testcase, num start) {
    var sum = 0;
    var end = start;
    var group = <num>[];
    do {
      end++;
      group = mylist.sublist(start, end);
      sum = group.fold(0, (prev, element) => prev + element);
    } while (sum < testcase);
    return sum == testcase ? group : [];
  }

  @override
  Future<void> a({bool test}) async {
    var filename = (test ?? false) ? classStringTest : classString;
    await init(filename, test);
    for (index = preamble; index < mylist.length && testGroup(index); index++);
    if (index < mylist.length) {
      answerA = mylist[index];
    } else {
      print('past end');
    }
  }

  @override
  Future<void> b({bool test}) async {
    var filename = (test ?? false) ? classStringTest : classString;
    await init(filename, test);
    index = 0;
    for (index = 0; index < mylist.length; index++) {
      var mysum = sumTest(answerA, index);
      if (mysum. isNotEmpty) {
        mysum.sort();
        answerB = mysum.first + mysum.last;
        break;
      }
    }
  }
}