Dodgy 2018 Day 20

2018/day20.py

@@ -0,0 +1,29 @@
+with open('day20-input', 'r') as file:
+  data = [l.strip('\n') for l in file]
+input = data[0][1:-1]
+from math import inf
+
+directions = {'N': 0-1j, 'E': 1+0j, 'S': 0+1j, 'W': -1+0j}
+stack = []
+distances = {0+0j: 0}
+pos = 0+0j
+next_distance = 1
+for c in input:
+  if c in directions:
+    pos += directions[c]
+    distances[pos] = min(distances.get(pos, inf), next_distance)
+    # This doesn't account for potentially shorter distances to other rooms along the old path to this room.
+    # Works for both parts on this input though so no gain in fixing v(ツ)v
+    # Backtracking those nodes would require keeping track of doors vs walls etc.
+  elif c == '(':
+    stack += [pos]
+  elif c == '|':
+    pos = stack[-1]
+  elif c == ')':
+    pos = stack.pop()
+  next_distance = distances[pos] + 1
+
+print(max(distances.values()))  # Part 1
+print(len([x for x in distances.values() if x >= 1000]))  # Part 2
+
+