public string Solve(string input)
{
(char[] Map, int yOffset)map = MapParser.Parse(input);
// Predictably, part 2 is just part 1 amped up. Equally predictably, this means
// that after a certain amount of time, the pattern will settle into a loop. This
// means we need to:
// 1. Work out the point at which we start iterating.
// 2. Find the iteration length.
// 3. Do some maths
// 4. Iterate a few more times
var states = new List <string>(10000);
string mapMemo = map.Memoize();
do
{
states.Add(mapMemo);
map = map.GetNextState();
mapMemo = map.Memoize();
}while (!states.Contains(mapMemo));
Console.WriteLine($"Iteration point hit after {states.Count} iterations");
// We've hit a point where we've seen this state before.
int originalIterationForThisState = states.IndexOf(mapMemo);
int iterationLength = states.Count - originalIterationForThisState;
const int target = 1000000000;
int numberOfWholeIterations = (target - originalIterationForThisState) / iterationLength;
int remainingTicksRequired = target - originalIterationForThisState - (numberOfWholeIterations * iterationLength);
for (int i = 0; i < remainingTicksRequired; i++)
{
map = map.GetNextState();
}
int woodCount = map.Map.Count(x => x == MapAcre.Trees);
int lumberYardCount = map.Map.Count(x => x == MapAcre.Lumberyard);
return((woodCount * lumberYardCount).ToString());
}
public string Solve(string input)
{
(char[] Map, int yOffset)map = MapParser.Parse(input);
////Console.WriteLine("Initial state:");
////map.WriteToConsole();
for (int i = 0; i < 10; i++)
{
map = map.GetNextState();
////Console.WriteLine($"After {i + 1} minute:");
////map.WriteToConsole();
}
int woodCount = map.Map.Count(x => x == MapAcre.Trees);
int lumberYardCount = map.Map.Count(x => x == MapAcre.Lumberyard);
return((woodCount * lumberYardCount).ToString());
}
