Add solution for 2021 day 12

2021/README.md

@@ -15,7 +15,7 @@
 | 09  |   ✓    |   ✓    | [C]       |
 | 10  |   ✓    |   ✓    | [OCaml]   |
 | 11  |   ✓    |   ✓    | [Crystal] |
-| 12  |        |        |           |
+| 12  |   ✓    |   ✓    | [Python]  |
 | 13  |        |        |           |
 | 14  |        |        |           |
 | 15  |        |        |           |
@@ -47,3 +47,4 @@
 [c]: http://www.open-std.org/jtc1/sc22/wg14
 [ocaml]: https://ocaml.org
 [crystal]: https://crystal-lang.org
+[python]: https://www.python.org

2021/day-12/.gitignore

@@ -0,0 +1,2 @@
+*.pyc
+*.pyo

2021/day-12/Justfile

@@ -0,0 +1,5 @@
+@part PART INPUT_FILE="inputs/puzzle.txt":
+    python3 part_{{PART}}.py {{INPUT_FILE}}
+
+clean:
+    rm -rf __pycache__

2021/day-12/common.py

@@ -0,0 +1,21 @@
+def cave_is_small(cave: str) -> bool:
+    return cave.islower()
+
+
+def add_connection(cave_system, a: str, b: str):
+    if a not in cave_system.keys():
+        cave_system[a] = set([b])
+    else:
+        cave_system[a].add(b)
+
+
+def parse_file(path: str):
+    cave_system = {}
+
+    with open(path, "r") as f:
+        for line in f.readlines():
+            cave_a, cave_b = line.strip().split("-")
+            add_connection(cave_system, cave_a, cave_b)
+            add_connection(cave_system, cave_b, cave_a)
+
+    return cave_system

2021/day-12/inputs/puzzle.txt

@@ -0,0 +1,22 @@
+xx-xh
+vx-qc
+cu-wf
+ny-LO
+cu-DR
+start-xx
+LO-vx
+cu-LO
+xx-cu
+cu-ny
+xh-start
+qc-DR
+vx-AP
+end-LO
+ny-DR
+vx-end
+DR-xx
+start-DR
+end-ny
+ny-xx
+xh-DR
+cu-xh

2021/day-12/inputs/sample1.txt

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

2021/day-12/inputs/sample2.txt

@@ -0,0 +1,10 @@
+dc-end
+HN-start
+start-kj
+dc-start
+dc-HN
+LN-dc
+HN-end
+kj-sa
+kj-HN
+kj-dc

2021/day-12/inputs/sample3.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

2021/day-12/part_one.py

@@ -0,0 +1,47 @@
+#!/usr/bin/env python3
+
+from common import parse_file, cave_is_small
+
+
+def search_paths(cave_system, cave="start", marked = set(), paths = [], path = []):
+    path = [*path, cave]
+
+    if cave == "end":
+        return [*paths, path]
+
+    if cave_is_small(cave):
+        marked.add(cave)
+
+    for connected_cave in cave_system[cave]:
+        if connected_cave in marked:
+            continue
+
+        paths = search_paths(cave_system, connected_cave, set(marked), paths, path)
+
+    return paths
+
+
+def short_path_filter(path):
+    small_caves = []
+
+    for cave in path[1:-1]:
+        if not cave_is_small(cave):
+            if cave in small_caves:
+                return False
+            small_caves.append(cave)
+
+    return True
+
+
+def only_short_paths(paths):
+    return list(filter(short_path_filter, paths))
+
+
+if __name__ == "__main__":
+    import sys
+
+    cave_system = parse_file(sys.argv[1])
+
+    paths = search_paths(cave_system)
+
+    print(len(only_short_paths(paths)))

2021/day-12/part_two.py

@@ -0,0 +1,37 @@
+#!/usr/bin/env python3
+
+from common import parse_file, cave_is_small
+
+
+def search_paths(cave_system, cave="start", marked = set(), paths = [], path = [], revisit = True):
+    path = [*path, cave]
+
+    if cave == "end":
+        return [*paths, path]
+
+    if cave_is_small(cave):
+        if cave in marked and revisit:
+            revisit = False
+
+        marked.add(cave)
+
+    for connected_cave in cave_system[cave]:
+        if connected_cave == "start":
+            continue
+
+        if connected_cave in marked and not revisit:
+            continue
+
+        paths = search_paths(cave_system, connected_cave, set(marked), paths, path, revisit)
+
+    return paths
+
+
+if __name__ == "__main__":
+    import sys
+
+    cave_system = parse_file(sys.argv[1])
+
+    paths = search_paths(cave_system)
+
+    print(len(paths))

README.md

@@ -8,4 +8,4 @@
 -   [2018](2018/README.md) (0% completed)
 -   [2019](2019/README.md) (0% completed)
 -   [2020](2020/README.md) (20% completed)
--   [2021](2021/README.md) (44% completed)
+-   [2021](2021/README.md) (48% completed)