static int B(string[] input)
{
const int MAX_GENERATION = 1_000_000_000;
Dictionary <int, int> seenValues = new Dictionary <int, int>();
var area = CollectionArea.FromInput(input);
while (area.Generation < MAX_GENERATION)
{
area.Step();
if (area.Generation > 1000)
{
if (seenValues.ContainsKey(area.Value()))
{
var gen = area.Generation;
var prevGen = seenValues[area.Value()];
var gendiff = gen - prevGen;
var skipSteps = (MAX_GENERATION - area.Generation) / gendiff;
area.SkipForward(skipSteps * gendiff);
}
else
{
seenValues[area.Value()] = area.Generation;
}
}
}
return(area.Value());
}
public static CollectionArea FromInput(string[] input)
{
var area = new CollectionArea(input.Length)
{
Generation = 0,
};
for (int row = 1; row < input.Length + 1; row++)
{
for (int column = 1; column < input.Length + 1; column++)
{
area.acres[row, column] = parseAcre(input[row - 1][column - 1]);
}
}
return(area);
acre parseAcre(char c)
{
switch (c)
{
case '.': return(acre.open);
case '|': return(acre.wood);
case '#': return(acre.lumberyard);
default:
throw new Exception("parse error");
}
}
}
static int A(string[] input, bool debug = false)
{
var area = CollectionArea.FromInput(input);
if (debug)
{
Console.WriteLine(area.ToString());
}
for (int i = 0; i < 10; i++)
{
area.Step();
if (debug)
{
Console.WriteLine(area.ToString());
}
}
return(area.Value());
}