protected override int Part2(string[] input)
{
var map = new CharMap();
var lines = input;
for (var y = 0; y < lines.Length; y++)
{
var line = lines[y];
for (var x = 0; x < line.Length; x++)
{
map[x][y] = line[x];
}
}
var width = 5;
var height = 5;
var levels = new List <CharMap>
{
map
};
var center = Point.From(2, 2);
for (var t = 0; t < 200; t++)
{
if (levels.First().AllPoints(c => c == '#').Any(p => p.X == 0 || p.Y == 0 || p.X == width - 1 || p.Y == height - 1))
{
var outer = new CharMap('.');
for (var x = 0; x < width; x++)
{
for (var y = 0; y < height; y++)
{
outer[x][y] = '.';
}
}
levels.Insert(0, outer);
}
var lowestlevel = levels.Last();
if (center.LookAround().Any(p => lowestlevel[p] == '#'))
{
var inner = new CharMap('.');
for (var x = 0; x < width; x++)
{
for (var y = 0; y < height; y++)
{
inner[x][y] = '.';
}
}
levels.Add(inner);
}
// Now go to work, one outer and its inner at a time
var nextlevels = new List <CharMap>();
for (var i = 0; i < levels.Count(); i++)
{
var outer = i > 0 ? levels[i - 1] : null;
var level = levels[i];
var inner = i < levels.Count() - 1 ? levels[i + 1] : null;
var innerBugs = inner?.AllPoints(c => c == '#').ToArray();
var nextmap = new CharMap();
foreach (var pos in level.AllPoints().Where(p => p != center)) // ToArray should not be needed?
{
var n = DirectionExtensions.LookAroundDirection().Select(d => BugsInDirection(outer, level, innerBugs, pos, d)).Sum();
var isOnBug = level[pos] == '#';
nextmap[pos] = isOnBug
? n == 1 ? '#' : '.'
: n == 1 || n == 2 ? '#' : '.';
}
nextlevels.Add(nextmap);
}
levels = nextlevels;
//Console.WriteLine();
//Console.WriteLine($"After {t} minutes");
//var leveldepth = lowest;
//foreach (var l in levels)
//{
// Console.WriteLine($"Depth {leveldepth++}:");
// l.ConsoleWrite(false);
// Console.WriteLine();
//}
//Console.WriteLine($"{levels.Count} levels, lowest={lowest}");
//Console.ReadLine();
}
var bugs = levels.Sum(l => l.AllPoints(c => c == '#').Count());
return(bugs);
int BugsInDirection(CharMap outer, CharMap level, Point[] innerBugs, Point pos0, Direction direction)
{
var pos = pos0.Move(direction);
if (pos.X < 0)
{
return(outer?[center.Left] == '#' ? 1 : 0);
}
if (pos.X >= width)
{
return(outer?[center.Right] == '#' ? 1 : 0);
}
if (pos.Y < 0)
{
return(outer?[center.Up] == '#' ? 1 : 0);
}
if (pos.Y >= height)
{
return(outer?[center.Down] == '#' ? 1 : 0);
}
if (pos == center)
{
switch (direction)
{
case Direction.Down: return(innerBugs?.Count(p => p.Y == 0) ?? 0);
case Direction.Left: return(innerBugs?.Count(p => p.X == width - 1) ?? 0);
case Direction.Up: return(innerBugs?.Count(p => p.Y == height - 1) ?? 0);
case Direction.Right: return(innerBugs?.Count(p => p.X == 0) ?? 0);
}
}
return(level[pos] == '#' ? 1 : 0);
}
//IEnumerable<CharMap> PaddedLevels(IEnumerable<CharMap> maps)
//{
// yield return new CharMap('.');
// foreach (var m in maps)
// {
// yield return m;
// }
// yield return new CharMap('.');
//}
//Console.WriteLine($"Day 24 Puzzle 2: {}");
//Debug.Assert(beampoints == 141);
}