Add day12

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

day12/day12.py

@@ -0,0 +1,87 @@
+#!/usr/bin/env python3
+import sys
+from collections import defaultdict
+from copy import deepcopy
+from typing import DefaultDict, MutableMapping, Set
+import pprint
+import string
+
+
+Vertices = DefaultDict[str, Set[str]]
+SMALL = set(string.ascii_lowercase)
+BIG = set(string.ascii_uppercase)
+
+
+def is_small(cave: str):
+    s = set(cave)
+    return (s & SMALL) == s
+
+
+def part1(vertices: Vertices):
+    small = {cave for cave in vertices.keys() if is_small(cave)}
+    big = set(vertices.keys()) - small
+    assert len(big & small) == 0
+
+    def find_paths(current: str, visited: Set[str] = set(), path: str = "") -> Set[str]:
+        visited = deepcopy(visited)
+        visited |= {current}
+        paths = set()
+        for vertex in vertices[current]:
+            if vertex == "end":
+                paths |= {path}
+            elif vertex in visited and vertex in small:
+                continue
+            else:
+                paths |= find_paths(vertex, visited, path + vertex)
+        return paths
+
+    paths = find_paths("start")
+    print(len(paths))
+
+
+def part2(vertices: Vertices):
+    small = {cave for cave in vertices.keys() if is_small(cave)}
+    big = set(vertices.keys()) - small
+    assert len(big & small) == 0
+
+    def find_paths(
+        allowed: str,
+        current: str,
+        visited: MutableMapping[str, int] = defaultdict(lambda: 0),
+        path: str = "",
+    ) -> Set[str]:
+        if current == allowed:
+            if visited[current] >= 2:
+                # This is a small cave and we've already visited it twice
+                return set()
+        elif current in small and visited[current]:
+            # Visited already
+            return set()
+        visited = deepcopy(visited)
+        visited[current] += 1
+        paths = set()
+        for vertex in vertices[current]:
+            if vertex == "end":
+                paths |= {path}
+            else:
+                paths |= find_paths(allowed, vertex, visited, path + vertex)
+        return paths
+
+    paths = set()
+    for allowed in small - {"start", "end"}:
+        paths |= find_paths(allowed, "start")
+    print(len(paths))
+
+
+# Doing this comprehension so Mypy is happy
+edges = [(a, b) for a, b in map(lambda l: l.strip().split("-"), sys.stdin)]
+vertices: Vertices = defaultdict(set)
+for a, b in edges:
+    vertices[a] |= {b}
+    vertices[b] |= {a}
+
+
+print("Part 1")
+part1(vertices)
+print("Part 2")
+part2(vertices)

day12/example.txt

@@ -0,0 +1,7 @@
+start-A
+start-b
+A-c
+A-b
+b-d
+A-end
+b-end

day12/example2.txt

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+dc-end
+HN-start
+start-kj
+dc-start
+dc-HN
+LN-dc
+HN-end
+kj-sa
+kj-HN
+kj-dc

day12/example3.txt

@@ -0,0 +1,18 @@
+fs-end
+he-DX
+fs-he
+start-DX
+pj-DX
+end-zg
+zg-sl
+zg-pj
+pj-he
+RW-he
+fs-DX
+pj-RW
+zg-RW
+start-pj
+he-WI
+zg-he
+pj-fs
+start-RW

day12/input.txt

@@ -0,0 +1,21 @@
+ma-start
+YZ-rv
+MP-rv
+vc-MP
+QD-kj
+rv-kj
+ma-rv
+YZ-zd
+UB-rv
+MP-xe
+start-MP
+zd-end
+ma-UB
+ma-MP
+UB-xe
+end-UB
+ju-MP
+ma-xe
+zd-UB
+start-xe
+YZ-end