public override object Part2(string input)
{
var numbers = input.ToLines()
.Select(long.Parse)
.OrderByDescending(x => x)
.ToArray();
var parts = new long[3];
if (!SumN.Find(numbers, 2020, ref parts))
{
throw new Exception("Panic! Unable to solve");
}
return(parts.Aggregate((x, y) => x * y));
}
private static long FindInvalidNumber(long[] numbers, Range search)
{
while (true)
{
var preamble = numbers[search]
.OrderByDescending(x => x)
.ToArray();
var parts = new long[2];
if (!SumN.Find(preamble, numbers[search.End], ref parts))
{
return(numbers[search.End]);
}
search = (search.Start.Value + 1)..(search.End.Value + 1);
}
}
