Add solution for day 18

Author: Simon Hessner

day18/example

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+.#.#...|#.
+.....#|##|
+.|..|...#.
+..|#.....#
+#.#|||#|#|
+...#.||...
+.|....|...
+||...#|.#|
+|.||||..|.
+...#.|..|.

day18/input

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+.|#..|#.|.|.|..###.|.##.|#.#...|##|#|#....|.#.#|.|
+.##..#.|#.||#.###.....#.......|....#|..|....#.#.#|
+....|...#..|||##..||......|.|..#.#......#.#|.#....
+..#..||..###.||#.#..#.|#.......#.|...#..|..#......
+|#.|..#|..##..#.#..#.|.|#|||.#.|...##||.|...|..##.
+#|#.....#|#...#...|.#|.|.##.|#|....#|.....#.||.#.#
+.........|.|.##.|##.|.#|.#..#.|#......||#........#
+..#..||#......|##|.|.#.........#.|.|#...|......|#.
+|..|.|.#.||#||.##|#..#..|.....||#||#|..||#........
+|.|.....|.#||#.#....|#.#|||.#|##..##|..|..|...||.|
+.#.#.||....#...|.|.#.#....#.#|#..#...##.....|..#|.
+#.##|...|.....#|.##.#..|.#.........#.|....|.|#|..|
+||#....#..|#|..|....|.#..||.#...||.|.||.#...#.#|..
+#....#..|#.|#..|###..#.|.##.|.#...|#..####.|..#|..
+|..|#|..#.....|....###..|#|...|..|.|#.##|....#...|
+#||#.#..|..#.#|.|...#..#|.#.|#.|....##...|.#.##...
+#|..#....|.|.#.|....#..##..#|.|||..|......#.......
+.|....|#..#.|..#.#..||#.#|#..|.|...||||.#.##......
+.#....|..#.#..#......||.#..|.|#.|#..|#.#...##.||..
+...|..|#......|..#.......|.|..#.|#.|......#...|#.#
+.|.........#.||...|..||..##.||...#...#..#...|#..#|
+.#|#.#|||.||...#.....|||..||.#.|..|.#.||.|.#......
+.#....##|.....#.||.###|..#.........|.#.....|...#.|
+#.|#.#....|....||...#.||.|#.|#...#||.#|.||.|...#.#
+.||..|...#.|#...||#|#..|....#....|.#..#....||...#.
+..#.#|....#||.|...##.|......#..#...||.|####.#.|.|.
+|.||#.|.|.#|....#.#...##...|.|.##|.#..|..#....|...
+........##|.|.#.##....||..##.#|#.|..#.|##.|.|.|..|
+.##....#|#|..##....|.....|.|..#||..#|#..#....||..#
+....|...|...#.|||#||..#.|.|......#|..##.|.|.......
+.....#..|.||#|###|..|.|...#.#...|.|.......#|...|##
+...|..|.#||..#||#..|..#..##|.|......||......|.....
+|....||.|#...|#......|....#..##|..|.....#..#.|...#
+.||.|......#....#......#.||.#..|#....#.#.||.|.#.|.
+.#|##..##|.|...#|##.##.#.#...|..##||.|#.##.|##..##
+|#.|.##....|...#.#.#.#.##.|..#.##|...|.#..|#.|#...
+#.|......#..|.|..##.||.||.||...#.#.|..|....#...#..
+.###.#|.|...|..#|....||||.#.#|......|...#....|.##.
+.|.|......|...........#.#..#|...|...|..||..##||#.|
+.|#.||.#|.#|.|...#|#|.......##|...|.#.##.#..|...|#
+####......#.#|.|.|.|##|.|.#..##|#.##..#|.##||...|.
+.....#.#.|#..||.........|##....|##.||...|.#|.....#
+..#|#...#..#.##....|#|#||##..|##...#||.#.....#....
+#.|...|...#.#...##.#.##|..||...|#......##..#..||||
+..#..##|#|.##...#.|..|.#..#.#|........|......|.#..
+.......||||#...#.......|..#|....|#..|#..#.#.....#.
+.|..|..||........|.....|.#.|..|...#....|...|...##.
+#...#.|...#..#...#||.#..#...........#.....#||.#...
+#.|.#.###.....#.||....#|.#|##...|#|#..|......#....
+..##|##....#|.||#..#........##.#......||...#.|....

day18/solution.py

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+# https://adventofcode.com/2018/day/18
+
+from collections import Counter
+OPEN = "."
+TREES = "|"
+LUMBERYARD = "#"
+
+def get_neighbors(x,y):
+	ans = []
+	for _x in range(x-1, x+2):
+		for _y in range(y-1, y+2):
+			if (_x,_y) != (x,y) and _x in range(0,50) and _y in range(0,50):
+				ans.append((_x,_y))
+	return ans
+
+def get_types(grid, coords):
+	ans = []
+	for x,y in coords:
+		ans.append(grid[y][x])
+	return ans
+
+def get_counts(elems):
+	c = Counter(elems)
+	return c[OPEN], c[TREES], c[LUMBERYARD]
+
+def convert(grid, x,y):
+	nbrs = get_types(grid, get_neighbors(x,y))
+	n_open, n_trees, n_lumberyard = get_counts(nbrs)
+
+	if grid[y][x] == OPEN:
+		if n_trees >= 3:
+			return TREES
+	elif grid[y][x] == TREES:
+		if n_lumberyard >= 3:
+			return LUMBERYARD
+	elif grid[y][x] == LUMBERYARD:
+		if n_trees < 1 or n_lumberyard < 1:
+			return OPEN
+	return grid[y][x]
+
+mapgrid = lambda grid: [[convert(grid,x,y) for x in range(50)] for y in range(50)]
+
+def part1():
+	with open('input') as f:
+		grid = list(map(list, f.read().splitlines()))
+		for _ in range(10):
+			grid = mapgrid(grid)
+			
+		_, n_trees, n_lumberyard = get_counts(sum(grid, []))
+		return n_trees*n_lumberyard
+
+def part2():
+	seen = []
+	lastlen = 0
+	
+	with open('input') as f:
+		grid = list(map(list, f.read().splitlines()))
+		repeating = False
+
+		t = 0
+		offset = 0
+		while not repeating:
+			t += 1
+			grid = mapgrid(grid)			
+			_, wood, lumb = get_counts(sum(grid, []))
+			v = wood*lumb
+
+			if v in seen:
+				if len(seen) == lastlen:
+					repeating = True
+					tmpv = v
+				else:
+					offset = t
+				lastlen = len(seen)
+			else:
+				seen.append(v)
+
+		period = False
+		periodic_values = {}
+		while not period:
+			t += 1
+			grid = mapgrid(grid)			
+			_, wood, lumb = get_counts(sum(grid, []))
+			v = wood*lumb
+			if v == tmpv:
+				period = True
+				period_length = t-offset-1
+			periodic_values[t] = v
+
+		periodic_values = {(t-offset)%period_length:v for t,v in periodic_values.items()}
+
+		return periodic_values[(1000000000-offset)%period_length]
+
+print("Part 1", part1())
+print("Part 2", part2())