2023.08 usable

challenges/2023/08-hauntedWasteland/main.py

@@ -1,6 +1,7 @@
 import sys
 import re
 from functools import reduce
+import math
 
 
 def parse(instr: str) -> tuple[str, dict[str, tuple[str, str]]]:
@@ -41,7 +42,7 @@ def two(instr: str):
         if key[-1] == "A":
             cursors.append(key)
 
-    constraints = []
+    loop_lengths = []
 
     for start in cursors:
         cursor = start
@@ -60,47 +61,11 @@ def two(instr: str):
         assert reduce(lambda acc, v: acc or v[0][-1] == "Z", history, False), f"{start} has no end condition"
 
         loop_start_key = (cursor, instruction_step)
-
-        endpoint_at = None
-        for key in history:
-            if key[0][-1] == "Z":
-                endpoint_at = history[key]
-                _debug(key)
-
         loop_starts_at = history[loop_start_key]
-        loop_length = (max(history.values()) - loop_starts_at) + 1
 
-        _debug(f"{start} loops {loop_start_key} {loop_starts_at=} {endpoint_at=} {loop_length=}")
+        loop_lengths.append((max(history.values()) - loop_starts_at) + 1)
     
-        constraints.append((loop_starts_at, endpoint_at - loop_starts_at, loop_length))
-
-    m = 0
-    soln = None
-
-    while True:
-        # _debug("---")
-
-        if m % 1000 == 0:
-            _debug(m, end="\r")
-
-        works = True
-
-        for (s, i, l) in constraints:
-            x = (m-s-i)/l
-
-            # _debug((s, i, l), x, (x < 0 or x % 1 != 0))
-
-            if x < 0 or not float(x).is_integer():
-                works = False
-                break
-
-        if works:
-            soln = m
-            break
-
-        m += 1
-
-    return soln
+    return math.lcm(*loop_lengths)
 
 
 def _debug(*args, **kwargs):