Solve 2021 day 12-14

2021/d12.py

@@ -0,0 +1,56 @@
+from lib import get_data
+from lib import Grid2D
+from lib import ints
+from collections import deque
+from collections import defaultdict
+
+data = get_data(__file__).strip()
+g = defaultdict(list)
+
+
+for line in data.splitlines():
+    a, b = line.strip().split("-")
+    g[a].append(b)
+    g[b].append(a)
+
+
+def no_doubles(path):
+    path = [p for p in path if p.islower()]
+    return len(path) == len(set(path))
+
+
+for part in [1, 2]:
+    start = ("start", ())
+    visited = set()
+    queue = deque([start])
+
+    total = 0
+    while queue:
+        vertex = queue.popleft()
+        if vertex in visited:
+            continue
+        visited.add(vertex)
+
+        current, path = vertex
+
+        neighbors = []
+        for neighbor in g[current]:
+            if neighbor == "end":
+                total += 1
+            elif neighbor == "start":
+                continue
+            elif neighbor.islower():
+                if neighbor not in path or (part == 2 and no_doubles(path)):
+                    new_path = tuple(list(path) + [neighbor])
+                    nb = (neighbor, new_path)
+                    if nb not in visited:
+                        queue.append(nb)
+            elif neighbor.isupper():
+                new_path = tuple(list(path) + [neighbor])
+                nb = (neighbor, new_path)
+                if nb not in visited:
+                    queue.append(nb)
+            else:
+                assert False
+
+    print(total)