day 17

Author: startrekdude

Diff for: 17/sample-input.txt

@@ -0,0 +1 @@
+>>><<><>><<<>><>>><<<>>><<<><<<>><>><<>>

Diff for: 17/solve.py

@@ -0,0 +1,147 @@
+from itertools import cycle
+from sys import argv as args
+
+ROCKS = [
+	[[1, 1, 1, 1]],
+	[
+		[0, 1, 0],
+		[1, 1, 1],
+		[0, 1, 0],
+	],
+	[
+		[0, 0, 1],
+		[0, 0, 1],
+		[1, 1, 1],
+	],
+	[
+		[1],
+		[1],
+		[1],
+		[1],
+	],
+	[
+		[1, 1],
+		[1, 1],
+	]
+]
+
+path = args[1] if len(args) >= 2 else "sample-input.txt"
+with open(path) as f:
+	lines = f.read().splitlines()
+
+class Rock:
+	def __init__(self, shape):
+		self.shape = shape
+	def place(self, highest_y):
+		self.x = 2
+		self.y = len(self.shape) + 3 + highest_y
+	def cells(self):
+		dx = 0
+		dy = 0
+		for line in self.shape:
+			for c in line:
+				yield c, self.x + dx, self.y + dy
+				dx += 1
+			
+			dx = 0
+			dy -= 1
+	def push(self, jet, room):
+		delta = 1 if jet == ">" else -1
+		for c, x, y in self.cells():
+			x += delta
+			if c == 1 and (x > 6 or x < 0 or room[y][x]):
+				return
+		self.x += delta
+	def fall(self, room):
+		for c, x, y in self.cells():
+			y -= 1
+			if c == 1 and (y < 0 or room[y][x]):
+				return True
+		self.y -= 1
+		return False
+	def draw_on(self, room):
+		for c, x, y in self.cells():
+			if c == 1:
+				room[y][x] = 1
+
+jeti = 0
+rocks = cycle(ROCKS)
+room = [[0] * 7 for _ in range(10_000)]
+highest_y = -1
+
+def next_jet():
+	global jeti
+	result = lines[0][jeti]
+	jeti += 1
+	jeti %= len(lines[0])
+	return result
+
+def fall():
+	global room, highest_y
+	
+	rock = Rock(next(rocks))
+	rock.place(highest_y)
+	while True:
+		rock.push(next_jet(), room)
+		stopped = rock.fall(room)
+		if stopped:
+			break
+	rock.draw_on(room)
+	if rock.y > highest_y:
+		highest_y = rock.y
+
+for _ in range(2022):
+	fall()
+print(highest_y + 1)
+
+jeti = 0
+rocks = cycle(ROCKS)
+room = [[0] * 7 for _ in range(1_000_000)]
+highest_y = -1
+
+fingerprints = {}
+
+rocks_fell = 0
+while rocks_fell < 1000000000000:
+	fall()
+	rocks_fell += 1
+	
+	fp_jeti  = jeti % len(lines[0])
+	fp_rocks = rocks_fell % len(ROCKS)
+	
+	hitmap = [0] * 7
+	iy = highest_y
+	while iy > 0:
+		row = room[iy]
+		for i, c in enumerate(row):
+			hitmap[i] += c
+		if all(c >= 1 for c in hitmap):
+			break
+		iy -= 1
+	
+	if iy == 0:
+		continue
+	
+	fpthis = room[iy:highest_y + 1]
+	fpkey = (fp_jeti, fp_rocks)
+	if fpkey in fingerprints:
+		fpold, old_rocks_fell, old_highest_y = fingerprints[fpkey]
+		if fpold == fpthis and fpkey == (1411, 2):
+			print(fpkey, fpold)
+			print(old_rocks_fell, old_highest_y)
+			print(rocks_fell, highest_y)
+			drocks = rocks_fell - old_rocks_fell
+			dhighest = highest_y - old_highest_y
+			print(drocks, dhighest)
+			can_apply = (1000000000000 - rocks_fell) // drocks
+			rocks_fell += can_apply * drocks
+			delta_highest = can_apply * dhighest
+			print(rocks_fell, dhighest)
+			#break
+	else:
+		if rocks_fell > 1972:
+			fingerprints[fpkey] = fpthis, rocks_fell, highest_y
+
+answer = delta_highest + highest_y + 1
+#assert answer == 1514285714288
+print(answer)

Diff for: README.md

@@ -22,4 +22,5 @@ Organized in a fairly self-explanatory way; `01` has the first day and so on. My
 | Day 14 | `00:18:18` | `00:21:25` |
 | Day 15 | `00:15:43` | `00:40:24` |
 | Day 16 | `04:06:04` | `10:09:10` |
+| Day 17 | `00:58:01` | `01:45:21` |