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diff --git a/2020/aoc2020-d24.py b/2020/aoc2020-d24.py
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+#advent of code 2020
+#day 24
+# https://www.redblobgames.com/grids/hexagons/
+# nested ifs in CheckAdjacent function aren't really slower than
+# making it a function, so i'm leaving it bc its more readable that way
+
+def CheckAdjacent(point, blackset):
+	black = 0;
+	py,px,pz = point;
+	for dkey in directions:
+		dx,dy,dz = directions[dkey];
+		p = (py+dy,px+dx, pz+dz);
+		if p in blackset: 
+			black += 1;
+	
+	if point in blackset:
+		if black == 0 or black > 2:
+			return False;
+		else: 
+			return True;
+	else:
+		if black == 2:
+			return True;
+		else:
+			return False;
+
+tilesteps = [];
+
+PuzzleInput = open("24.in","r")
+for line in PuzzleInput:
+	line = line.replace("\n","");
+	instructions = [];
+	i = 0;
+	while i < len(line):
+		if line[i] in ["n","s"]:
+			instructions.append(line[i:i+2]);
+			i += 2;
+		else:
+			instructions.append(line[i]);
+			i += 1;
+	tilesteps.append(instructions);
+PuzzleInput.close();
+
+directions = dict();
+directions["e"] = (1,0,-1);
+directions["w"] = (-1,0,1);
+directions["ne"] = (1,-1,0);
+directions["nw"] = (0,-1,1);
+directions["sw"] = (-1,1,0);
+directions["se"] = (0,1,-1);
+
+grid = dict();
+# 0 - white
+# 1 - black
+
+for tilestep in tilesteps:
+	p = (0,0,0);
+	for step in tilestep:
+		py,px,pz = p;
+		dy,dx,dz = directions[step];
+		p = (py+dy,px+dx, pz+dz);
+	grid[p] = ( grid.get(p,0) + 1)%2;
+
+blacks = set();
+part1 = 0;
+for g in grid:
+	if grid[g] == 1: 
+		part1 += 1;
+		blacks.add(g);
+
+print("part 1 =", part1);
+
+days = 100;
+for day in range(days):
+	NewBlacks = set();
+	for b in blacks:
+		if CheckAdjacent(b,blacks): NewBlacks.add(b);
+		for coord in directions.values():
+			n = (b[0] + coord[0],b[1] + coord[1],b[2] + coord[2]);
+			if CheckAdjacent(n,blacks): NewBlacks.add(n);
+	blacks = set();
+	blacks.update(NewBlacks);
+
+part2 = len(blacks);
+print("part 2 =", part2);