public string SolvePartA(IEnumerable <string> input, int capacity, int preamble)
{
SumsChecker sc = new SumsChecker(capacity);
IEnumerable <long> numbers = input
.Select <string, long?>(line => long.TryParse(line, out long n) ? n : null)
.Where(maybeInt => maybeInt.HasValue)
.Select(maybeInt => maybeInt.Value);
return(FindInvalidNumber(numbers, sc, preamble).ToString());
}
private long FindInvalidNumber(IEnumerable <long> numbers, SumsChecker checker, int preamble)
{
foreach (long n in numbers.Take(preamble))
{
checker.AddNumber(n);
}
foreach (long n in numbers.Skip(preamble))
{
if (!checker.Contains(n))
{
return(n);
}
checker.AddNumber(n);
}
return(-1);
}