import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.Map.Entry;
import java.util.concurrent.atomic.AtomicInteger;

public class Environment
	{
		Set<Point> livingCells;
		Map<Point, AtomicInteger> surroundingCells = new HashMap<Point, AtomicInteger>();
		Environment(Set<Point> ps) {
			livingCells = ps;
		}
		public Set<Point> getPoints()
		{
			return livingCells;
		}
		public Environment next()
		{
			Set<Point> newPoints = new HashSet<Point>();
			for (Entry<Point, AtomicInteger> s : surroundingCells.entrySet()) {
				if (s.getValue().intValue() == 2 || s.getValue().intValue() == 3) {
					if (livingCells.contains(s.getKey()) || s.getValue().intValue() == 3) {
						newPoints.add(s.getKey());
					}
				}
			}
			return new Environment(newPoints);
		}
		Object _lock = new Object();
		void increment(Point p)
		{
			for (Point q : p.neighbours()) {
				if (!surroundingCells.containsKey(q)) { 
					synchronized(_lock) {
						if (!surroundingCells.containsKey(q)) { surroundingCells.put(q, new AtomicInteger(1)); continue; }
					}
				}
				surroundingCells.get(q).incrementAndGet();
			}
		}
	}