internal int DistanceTo(NanoBot otherBot)
{
int dist = Math.Abs(this.X - otherBot.X);
dist += Math.Abs(this.Y - otherBot.Y);
dist += Math.Abs(this.Z - otherBot.Z);
return(dist);
}
public Day23() : base(2018, 23)
{
Regex botParse = new Regex(".*?<(-?\\d+),(-?\\d+),(-?\\d+)>, r=(-?\\d+)");
foreach (var s in InputLines)
{
var match = botParse.Match(s);
NanoBot bot = new NanoBot();
bot.X = int.Parse(match.Groups[1].Value);
bot.Y = int.Parse(match.Groups[2].Value);
bot.Z = int.Parse(match.Groups[3].Value);
bot.R = int.Parse(match.Groups[4].Value);
Bots.Add(bot);
}
}
/* Algorithm/explanation: https://www.reddit.com/r/adventofcode/comments/a8sqov/help_day_23_part_2_any_provably_correct_fast/ecfag7f */
internal override string SolvePart2()
{
PriorityQueue <NanoBot> q = new PriorityQueue <NanoBot>();
/* create a bot that has every other bot in range */
var maxRadius = Bots.Select(b => Math.Abs(b.X) + Math.Abs(b.Y) + Math.Abs(b.Z)).Max();
var searchBot = new NanoBot()
{
X = 0, Y = 0, Z = 0, R = maxRadius
};
var intersectCount = Bots.Where(b => b.Intersects(searchBot)).Count();
q.AddOrUpdate(searchBot, intersectCount);
while (q.Count > 0)
{
var maxPriority = q._priorities.Max();
searchBot = q._dataByPriority[maxPriority].OrderBy(d => d.DistanceTo(0, 0, 0)).OrderBy(d => d.R).First();
q.DequeueItem(searchBot);
if (searchBot.R <= 0)
{
return(searchBot.DistanceTo(0, 0, 0).ToString());
}
else
{
foreach (var bot in searchBot.SplitBot())
{
intersectCount = Bots.Where(b => b.Intersects(bot)).Count();
q.AddOrUpdate(bot, intersectCount);
}
}
}
return("??");
}
internal bool Intersects(NanoBot otherBot)
{
return(DistanceTo(otherBot) <= R + otherBot.R);
}