Solution to problem 17 in Python

src/2020/P17.py

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+# --- Day 17: Conway Cubes ---
+
+# As your flight slowly drifts through the sky, the Elves at the Mythical
+# Information Bureau at the North Pole contact you. They'd like some help
+# debugging a malfunctioning experimental energy source aboard one of their
+# super-secret imaging satellites.
+
+# The experimental energy source is based on cutting-edge technology: a set of
+# Conway Cubes contained in a pocket dimension! When you hear it's having
+# problems, you can't help but agree to take a look.
+
+# The pocket dimension contains an infinite 3-dimensional grid. At every
+# integer 3-dimensional coordinate (x,y,z), there exists a single cube which is
+# either active or inactive.
+
+# In the initial state of the pocket dimension, almost all cubes start
+# inactive. The only exception to this is a small flat region of cubes (your
+# puzzle input); the cubes in this region start in the specified active (#) or
+# inactive (.) state.
+
+# The energy source then proceeds to boot up by executing six cycles.
+
+# Each cube only ever considers its neighbors: any of the 26 other cubes where
+# any of their coordinates differ by at most 1. For example, given the cube at
+# x=1,y=2,z=3, its neighbors include the cube at x=2,y=2,z=2, the cube at
+# x=0,y=2,z=3, and so on.
+
+# During a cycle, all cubes simultaneously change their state according to the
+# following rules:
+
+#     If a cube is active and exactly 2 or 3 of its neighbors are also active,
+# the cube remains active. Otherwise, the cube becomes inactive.
+#     If a cube is inactive but exactly 3 of its neighbors are active, the cube
+# becomes active. Otherwise, the cube remains inactive.
+
+# The engineers responsible for this experimental energy source would like you
+# to simulate the pocket dimension and determine what the configuration of
+# cubes should be at the end of the six-cycle boot process.
+
+# For example, consider the following initial state:
+
+# .#.
+# ..#
+# ###
+
+# Even though the pocket dimension is 3-dimensional, this initial state
+# represents a small 2-dimensional slice of it. (In particular, this initial
+# state defines a 3x3x1 region of the 3-dimensional space.)
+
+# Simulating a few cycles from this initial state produces the following
+# configurations, where the result of each cycle is shown layer-by-layer at
+# each given z coordinate (and the frame of view follows the active cells in
+# each cycle):
+
+# Before any cycles:
+
+# z=0
+# .#.
+# ..#
+# ###
+
+
+# After 1 cycle:
+
+# z=-1
+# #..
+# ..#
+# .#.
+
+# z=0
+# #.#
+# .##
+# .#.
+
+# z=1
+# #..
+# ..#
+# .#.
+
+
+# After 2 cycles:
+
+# z=-2
+# .....
+# .....
+# ..#..
+# .....
+# .....
+
+# z=-1
+# ..#..
+# .#..#
+# ....#
+# .#...
+# .....
+
+# z=0
+# ##...
+# ##...
+# #....
+# ....#
+# .###.
+
+# z=1
+# ..#..
+# .#..#
+# ....#
+# .#...
+# .....
+
+# z=2
+# .....
+# .....
+# ..#..
+# .....
+# .....
+
+
+# After 3 cycles:
+
+# z=-2
+# .......
+# .......
+# ..##...
+# ..###..
+# .......
+# .......
+# .......
+
+# z=-1
+# ..#....
+# ...#...
+# #......
+# .....##
+# .#...#.
+# ..#.#..
+# ...#...
+
+# z=0
+# ...#...
+# .......
+# #......
+# .......
+# .....##
+# .##.#..
+# ...#...
+
+# z=1
+# ..#....
+# ...#...
+# #......
+# .....##
+# .#...#.
+# ..#.#..
+# ...#...
+
+# z=2
+# .......
+# .......
+# ..##...
+# ..###..
+# .......
+# .......
+# .......
+
+# After the full six-cycle boot process completes, 112 cubes are left in the
+# active state.
+
+# Starting with your given initial configuration, simulate six cycles. How many
+# cubes are left in the active state after the sixth cycle?
+
+import itertools as iter
+
+with open("files/P17.txt", "r") as f:
+    init_state = [line for line in f.read().strip().split("\n")]
+
+
+def get_active_points(dim: int):
+    ap = set()
+    for y, z in enumerate(init_state):
+        for x, c in enumerate(z):
+            if c == "#":
+                ap.add(tuple([x, y] + [0] * (dim - 2)))
+    return ap
+
+
+def part_1() -> None:
+    active_points = get_active_points(dim=3)
+    for it in range(6):
+        new_active_points = set()
+        # check x,y,z point
+        for x in range(-10 - it, it + 10):
+            for y in range(-10 - it, it + 10):
+                for z in range(-2 - it, it + 2):
+                    point = (x, y, z)
+
+                    # for the current point, check the neighbors
+                    num_actives = 0
+                    for delta in iter.product(range(-1, 2), repeat=3):
+                        if delta != (0,) * 3:
+                            if (
+                                tuple([a + b for a, b in zip(point, delta)])
+                                in active_points
+                            ):
+                                num_actives += 1
+
+                    # apply rules
+                    if point in active_points and (
+                        num_actives == 2 or num_actives == 3
+                    ):
+                        new_active_points.add(point)
+                    if point not in active_points and num_actives == 3:
+                        new_active_points.add(point)
+
+        # next iteration
+        active_points = new_active_points
+    print(f"After 6 cycles in 3D, we have {len(active_points)} active cubes")
+
+
+if __name__ == "__main__":
+    part_1()