Day 12 part 2

2019/day12.py

@@ -1,6 +1,8 @@
+from copy import deepcopy
 import itertools
 import re
 
+import numpy
 
 
 def main():
@@ -8,14 +10,33 @@ def main():
         lines = input_file.readlines()
     vector_re = re.compile(r"<x=(-?\d+), y=(-?\d+), z=(-?\d+)>")
     matches = [vector_re.match(line.rstrip()) for line in lines]
-    coords = [list([int(i) for i in match.groups()]) for match in matches]
-    moons = [[coord, [0] * 3] for coord in coords]
+    coords = [[int(i) for i in match.groups()] for match in matches]
+    moons_i = [[coord, [0] * 3] for coord in coords]
 
     # Part 1
+    moons = deepcopy(moons_i)
     for _ in range(1000):
         do_step(moons)
     print("Total moons energy:", sum(get_energy(moon) for moon in moons))
 
+    # Part 2
+    d_cycles = [0] * 3
+    for d in range(3):
+        moons = deepcopy(moons_i)
+        step = 0
+        found_d_cycle = False
+        while not found_d_cycle:
+            do_step(moons)
+            step += 1
+            for moon, moon_i in zip(moons, moons_i):
+                if moon[0][d] != moon_i[0][d] or moon[1][d] != moon_i[1][d]:
+                    break
+            else:
+                d_cycles[d] = step
+                found_d_cycle = True
+    print("Dimension cycles:", d_cycles)
+    print("LCM:", numpy.lcm.reduce(d_cycles))
+
 def do_step(moons):
     for a, b in itertools.combinations(moons, 2):
         for d in range(3):