day 12

12/12.py

@@ -0,0 +1,97 @@
+#!/usr/bin/env python3
+
+import sys, math
+
+moonvel = ([0,0,0], [0,0,0], [0,0,0], [0,0,0])
+
+# ex1
+# <x=-1, y=0, z=2>
+# <x=2, y=-10, z=-7>
+# <x=4, y=-8, z=8>
+# <x=3, y=5, z=-1>
+moonpos = ([-1,0,2], [2,-10,-7], [4,-8,8], [3,5,-1])
+
+# ex2
+# <x=-8, y=-10, z=0>
+# <x=5, y=5, z=10>
+# <x=2, y=-7, z=3>
+# <x=9, y=-8, z=-3>
+# moonpos = ([-8,-10,0], [5,5,10], [2,-7,3], [9,-8,-3])
+
+# p2 ex
+# <x=-8, y=-10, z=0>
+# <x=5, y=5, z=10>
+# <x=2, y=-7, z=3>
+# <x=9, y=-8, z=-3>
+moonpos = ([-8,-10,0], [5,5,10], [2,-7,3], [9,-8,-3])
+
+
+# mine
+# <x=5, y=13, z=-3>
+# <x=18, y=-7, z=13>
+# <x=16, y=3, z=4>
+# <x=0, y=8, z=8>
+moonpos = ([5,13,-3], [18,-7,13], [16,3,4], [0,8,8])
+
+seen={}
+axisperiod = {}
+axisstart = {}
+steps = 0
+gotmoons = 0
+go = True
+
+while go:
+
+    for axis in range(0, 3):
+        # Save state for each axis, when we see a repeat then we probably have a period and offset for that moon.
+        state = "%d: %d,%d,%d,%d,%d,%d,%d,%d" % (axis, moonpos[0][axis], moonpos[1][axis], moonpos[2][axis], moonpos[3][axis], moonvel[0][axis],moonvel[1][axis],moonvel[2][axis],moonvel[3][axis])
+        if state in seen and not axis in axisperiod:
+            print(steps, state, seen[state])
+            axisperiod[axis] = (steps - seen[state])
+            axisstart[axis] = seen[state]
+            print(axis, axisstart[axis], axisperiod[axis])
+            gotmoons += 1
+        seen[state] = steps
+
+    for moon in range(0, len(moonpos)):
+        # Update velocity
+        for pair in range(0, len(moonpos)):
+            if pair == moon:
+                continue
+            for coord in range(0,3):
+                if moonpos[moon][coord] < moonpos[pair][coord]:
+                    moonvel[moon][coord] += 1
+                elif moonpos[moon][coord] > moonpos[pair][coord]:
+                    moonvel[moon][coord] -= 1
+
+    # update position
+    for moon in range(0, len(moonpos)):
+        for coord in range(0,3):
+            moonpos[moon][coord] += moonvel[moon][coord]
+
+    steps += 1
+
+    if steps % 100000 == 0:
+        print("steps: " + str(steps) + "...")
+
+    if gotmoons == 3:
+        go = False
+
+# inefficient, but it'll do.
+def lcm(numbers):
+    snum = sorted(numbers)
+    bigly = snum.pop(-1)
+    current = bigly
+    c = range(0, len(snum))
+    while True:
+        test = True
+        for n in c:
+            if current % snum[n] != 0:
+                test = False
+            else:
+                continue
+        if test:
+            return current
+        current += bigly
+
+print(lcm((axisperiod[0],axisperiod[1],axisperiod[2])))