2023 day 12.

2023/day12.py

@@ -1,13 +1,107 @@
+import os
 import sys
-from collections import defaultdict
-from dataclasses import dataclass
+from functools import lru_cache
+from typing import Iterable
+
+VERBOSE = os.getenv("AOC_VERBOSE") == "True"
+
+
+@lru_cache
+def compute_fitting_arrangements(pattern: str, counts: tuple[int, ...]) -> int:
+    """
+    fn3p tries to fit ALL values in counts() inside the pattern.
+    """
+    # no pattern -> ok if nothing to fit, otherwise ko
+    if not pattern:
+        count = 1 if not counts else 0
+
+    # no count -> ok if pattern has no mandatory entry, else ko
+    elif not counts:
+        count = 1 if pattern.find("#") == -1 else 0
+
+    # cannot fit all values -> ko
+    elif len(pattern) < sum(counts) + len(counts) - 1:
+        count = 0
+
+    elif len(pattern) < counts[0]:
+        count = 0
+
+    else:
+        count = 0
+
+        if pattern[0] == "?":
+            count += compute_fitting_arrangements(pattern[1:], counts)
+
+        if len(pattern) == counts[0]:
+            count += 1
+
+        elif pattern[counts[0]] != "#":
+            count += compute_fitting_arrangements(pattern[counts[0] + 1 :], counts[1:])
+
+    return count
+
+
+@lru_cache
+def compute_possible_arrangements(
+    patterns: tuple[str, ...], counts: tuple[int, ...]
+) -> int:
+    if not patterns:
+        return 1 if not counts else 0
+
+    with_hash = sum(1 for p in patterns[1:] if p.find("#") >= 0)
+
+    if with_hash > len(counts):
+        return 0
+
+    to_fit = counts if with_hash == 0 else counts[:-with_hash]
+    remaining = () if with_hash == 0 else counts[-with_hash:]
+
+    if not to_fit:
+        if patterns[0].find("#") != -1:
+            return 0
+        return compute_possible_arrangements(patterns[1:], remaining)
+
+    elif patterns[0].find("#") != -1 and len(patterns[0]) < to_fit[0]:
+        return 0
+
+    elif patterns[0].find("?") == -1:
+        if len(patterns[0]) != to_fit[0]:
+            return 0
+        return compute_possible_arrangements(patterns[1:], counts[1:])
+
+    else:
+        return sum(
+            fp * compute_possible_arrangements(patterns[1:], to_fit[i:] + remaining)
+            for i in range(len(to_fit) + 1)
+            if (fp := compute_fitting_arrangements(patterns[0], to_fit[:i])) > 0
+        )
+
+
+def compute_all_possible_arrangements(lines: Iterable[str], repeat: int) -> int:
+    count = 0
+
+    if VERBOSE:
+        from tqdm import tqdm
+
+        lines = tqdm(lines)
+
+    for line in lines:
+        parts = line.split(" ")
+        count += compute_possible_arrangements(
+            tuple(filter(len, "?".join(parts[0] for _ in range(repeat)).split("."))),
+            tuple(int(c) for c in parts[1].split(",")) * repeat,
+        )
+
+    return count
+
 
 lines = sys.stdin.read().splitlines()
 
+
 # part 1
-answer_1 = ...
+answer_1 = compute_all_possible_arrangements(lines, 1)
 print(f"answer 1 is {answer_1}")
 
 # part 2
-answer_2 = ...
+answer_2 = compute_all_possible_arrangements(lines, 5)
 print(f"answer 2 is {answer_2}")

2023/tests/day12.txt

@@ -0,0 +1,6 @@
+???.### 1,1,3
+.??..??...?##. 1,1,3
+?#?#?#?#?#?#?#? 1,3,1,6
+????.#...#... 4,1,1
+????.######..#####. 1,6,5
+?###???????? 3,2,1