private static (Cup first, Cup last, IDictionary <long, Cup> lookup) ReadCups(string?fileName = null)
{
var labels = InputFile.ReadAllLines(fileName)
.Single()
.Select(s => (long)(s - '0'));
var lookup = new Dictionary <long, Cup>();
var first = (Cup?)null;
var last = first;
foreach (var label in labels)
{
var cup = new Cup(label);
cup.Next = first ??= cup;
if (last != null)
{
last.Next = cup;
}
last = cup;
lookup[label] = cup;
}
if (first is null || last is null)
{
throw new Exception("No cups found.");
}
return(first, last, lookup);
}
private static Cup PickUpNextThreeCups(Cup cup)
{
var firstRemoved = cup.Next;
var lastRemoved = firstRemoved.Next.Next;
cup.Next = lastRemoved.Next;
lastRemoved.Next = firstRemoved;
return(firstRemoved);
}
private static Cup FindNextDestination(Cup currentCup, Cup pickedUp, IDictionary <long, Cup> lookup)
{
long destinationLabel = currentCup.Label;
while (true)
{
if (--destinationLabel < 1)
{
destinationLabel = lookup.Count;
}
if (pickedUp.Label != destinationLabel &&
pickedUp.Next.Label != destinationLabel &&
pickedUp.Next.Next.Label != destinationLabel)
{
break;
}
}
return(lookup[destinationLabel]);
}
