static void Main(string[] args)
{
// part 1
var part_1_cups = "362981754".Select(c => Convert.ToInt64(c.ToString())).ToList();
move_cups(ref part_1_cups, 100);
var cups_after_one = new StringBuilder();
var output_cup_index = part_1_cups.IndexOf(1) + 1;
for (var i = 0; i < part_1_cups.Count - 1; i++, output_cup_index++)
{
if (output_cup_index == part_1_cups.Count)
{
output_cup_index = 0;
}
cups_after_one.Append(part_1_cups[output_cup_index].ToString());
}
Console.WriteLine(cups_after_one.ToString());
// part 2
var part_2_cups = "362981754".Select(c => Convert.ToInt64(c.ToString())).ToList();
var part_2_cup_dictionary = new Dictionary <long, CircularListNode>();
var part_2_cups_max = part_2_cups.Max();
var part_2_cups_min = part_2_cups.Min();
for (var i = part_2_cups_max + 1; i <= 1_000_000; i++)
{
part_2_cups.Add(i);
}
part_2_cups_max = 1_000_000;
var list_head = new CircularListNode(part_2_cups[0]);
var current_cup = list_head;
part_2_cup_dictionary[part_2_cups[0]] = list_head;
for (var i = 1; i < part_2_cups.Count; i++)
{
current_cup.Next = new CircularListNode(part_2_cups[i]);
current_cup = current_cup.Next;
part_2_cup_dictionary[part_2_cups[i]] = current_cup;
}
current_cup.Next = list_head;
move_cups(ref list_head, 10_000_000, part_2_cups_min, part_2_cups_max, part_2_cup_dictionary);
Console.WriteLine(part_2_cup_dictionary[1].Next.value * part_2_cup_dictionary[1].Next.Next.value);
}
// the fast way
static void move_cups(ref CircularListNode _current_cup, int _moves, long _min_value, long _max_value, Dictionary <long, CircularListNode> _cup_dictionary)
{
// perform moves
for (var i = 0; i < _moves; i++)
{
var triplet_head = _current_cup.Next;
_current_cup.Next = triplet_head.Next.Next.Next;
triplet_head.Next.Next.Next = null;
var destination_cup_value = _current_cup.value - 1;
while (
triplet_head.value == destination_cup_value ||
triplet_head.Next.value == destination_cup_value ||
triplet_head.Next.Next.value == destination_cup_value
)
{
destination_cup_value--;
}
if (destination_cup_value < _min_value)
{
destination_cup_value = _max_value;
}
while (
triplet_head.value == destination_cup_value ||
triplet_head.Next.value == destination_cup_value ||
triplet_head.Next.Next.value == destination_cup_value
)
{
destination_cup_value--;
}
var destination_cup_node = _cup_dictionary[destination_cup_value];
triplet_head.Next.Next.Next = destination_cup_node.Next;
destination_cup_node.Next = triplet_head;
_current_cup = _current_cup.Next;
}
}
public CircularListNode(long _value)
{
this.value = _value;
this.Next = null;
}
