enum Field { Empty, Tree, Lumber }
Dictionary mapping = new Dictionary
{
{'.', Field.Empty},
{'|', Field.Tree},
{'#', Field.Lumber},
};
int Width;
int Height;
Field[,] Map;
void Main()
{
Load(File.ReadAllLines(Path.Combine(Path.GetDirectoryName(Util.CurrentQueryPath), @"18_input.txt")));
//$"Initial state:".Dump();Dump();
var history = new Dictionary();
int gen=0;
for (;;)
{
Tick();
gen++;
var hash = Hash();
if (history.ContainsKey(hash))
{
int loop = gen-history[hash];
int remaining = 1000000000;
remaining -= gen;
var off = remaining % loop;
for (int i = 0; i < off; i++) { Tick(); gen++; }
$"After {gen} ticks there are {FullCount(Field.Tree)} trees and {FullCount(Field.Lumber)} lumbers, the score is {FullCount(Field.Tree) * FullCount(Field.Lumber)} and the state loops every {loop} generations".Dump();
return;
}
else
{
history[hash] = gen;
}
}
}
string Hash()
{
StringBuilder b = new StringBuilder();
for (int y = 0; y < Height; y++) for (int x = 0; x < Width; x++) b.Append((char)('0'+(int)Map[x, y]));
return b.ToString();
}
void Dump()
{
StringBuilder b = new StringBuilder();
for (int y = 0; y < Height; y++)
{
for (int x = 0; x < Width; x++)
{
if (Map[x, y] == Field.Empty) b.Append('.');
else if (Map[x, y] == Field.Tree) b.Append('|');
else if (Map[x, y] == Field.Lumber) b.Append('#');
else throw new Exception(".");
}
b.AppendLine();
}
b.ToString().Dump();
"".Dump();
}
void Load(string[] input)
{
Width = input[0].Length;
Height = input.Length;
Map = new Field[Width, Height];
for (var x = 0; x < Width; x++) for (var y = 0; y < Height; y++) Map[x, y] = mapping[input[y][x]];
}
void Tick()
{
var d = new Field[Width,Height];
for (var y = 0; y < Height; y++) for (var x = 0; x < Width; x++) Tick(ref Map, ref d, x, y);
Map=d;
}
void Tick(ref Field[,] src, ref Field[,] dst, int x, int y)
{
if (src[x,y] == Field.Empty)
{
dst[x,y] = (Count(ref src, x, y, Field.Tree) >= 3) ? Field.Tree : Field.Empty;
}
else if (src[x, y] == Field.Tree)
{
dst[x, y] = (Count(ref src, x, y, Field.Lumber) >= 3) ? Field.Lumber : Field.Tree;
}
else if (src[x, y] == Field.Lumber)
{
dst[x, y] = (Count(ref src, x, y, Field.Lumber) >= 1 && Count(ref src, x, y, Field.Tree) >= 1) ? Field.Lumber : Field.Empty;
}
}
int Count(ref Field[,] fld, int x, int y, Field s)
{
int c = 0;
if (x > 0 && y > 0 && fld[x - 1, y - 1] == s) c++;
if (x > 0 && fld[x - 1, y ] == s) c++;
if (x > 0 && y < Height-1 && fld[x - 1, y + 1] == s) c++;
if ( y < Height-1 && fld[x , y + 1] == s) c++;
if (x < Width-1 && y < Height-1 && fld[x + 1, y + 1] == s) c++;
if (x < Width-1 && fld[x + 1, y ] == s) c++;
if (x < Width-1 && y > 0 && fld[x + 1, y - 1] == s) c++;
if ( y > 0 && fld[x , y - 1] == s) c++;
return c;
}
int FullCount(Field f)
{
int c = 0;
for (var x = 0; x < Width; x++) for (var y = 0; y < Height; y++) if (Map[x,y]==f)c++;
return c;
}