2023/day12.py

@@ -1,17 +1,16 @@
-import itertools
+import os
 import sys
 from functools import lru_cache
-from typing import Iterator
+from typing import Iterable
 
-lines = sys.stdin.read().splitlines()
+VERBOSE = os.getenv("AOC_VERBOSE") == "True"
 
 
 @lru_cache
-def fn3p(pattern: str, counts: tuple[int, ...]) -> int:
+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
@@ -24,46 +23,30 @@ def fn3p(pattern: str, counts: tuple[int, ...]) -> int:
     elif len(pattern) < sum(counts) + len(counts) - 1:
         count = 0
 
+    elif len(pattern) < counts[0]:
+        count = 0
+
     else:
         count = 0
 
         if pattern[0] == "?":
-            count += fn3p(pattern[1:], counts)
+            count += compute_fitting_arrangements(pattern[1:], counts)
 
         if len(pattern) == counts[0]:
             count += 1
 
         elif pattern[counts[0]] != "#":
-            count += fn3p(pattern[counts[0] + 1 :], counts[1:])
+            count += compute_fitting_arrangements(pattern[counts[0] + 1 :], counts[1:])
 
     return count
 
 
 @lru_cache
-def fn3(pattern: str, counts: tuple[int, ...]) -> list[tuple[int, tuple[int, ...]]]:
-    # empty pattern
-    if not pattern:
-        return [(1, counts)]
-
-    elif not counts:
-        return [(1, ())] if pattern.find("#") == -1 else []
-
-    elif pattern.find("#") != -1 and len(pattern) < counts[0]:
-        return []
-
-    elif pattern.find("?") == -1 and counts[0] == len(pattern):
-        return [(1, counts[1:])]
-
-    else:
-        return [(fn3p(pattern, counts[:i]), counts[i:]) for i in range(len(counts) + 1)]
-
-
-@lru_cache
-def fn4(patterns: tuple[str], counts: tuple[int, ...], depth: int = 0) -> int:
+def compute_possible_arrangements(
+    patterns: tuple[str, ...], counts: tuple[int, ...]
+) -> int:
     if not patterns:
-        if not counts:
-            return 1
-        return 0
+        return 1 if not counts else 0
 
     with_hash = sum(1 for p in patterns[1:] if p.find("#") >= 0)
 
@@ -73,37 +56,52 @@ def fn4(patterns: tuple[str], counts: tuple[int, ...], depth: int = 0) -> int:
     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
-    for fp, fc in fn3(patterns[0], to_fit):
-        if fp == 0:
-            continue
-        # print("|" * depth, patterns[0], to_fit, remaining, fp, fc)
-        count += fp * fn4(patterns[1:], fc + remaining, depth + 1)
 
-    return count
+    if VERBOSE:
+        from tqdm import tqdm
 
-
-def v3(pattern: str, counts: list[int]) -> int:
-    blocks = list(filter(len, pattern.split(".")))
-    return fn4(tuple(blocks), tuple(counts))
-
-
-def compute_possible_arrangements(repeat: int) -> int:
-    count = 0
+        lines = tqdm(lines)
 
     for line in lines:
         parts = line.split(" ")
-        pattern = "?".join(parts[0] for _ in range(repeat))
-        counts = [int(c) for c in parts[1].split(",")] * repeat
-        count += v3(pattern, counts)
+        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 = compute_possible_arrangements(1)
+answer_1 = compute_all_possible_arrangements(lines, 1)
 print(f"answer 1 is {answer_1}")
 
 # part 2
-answer_2 = compute_possible_arrangements(5)
+answer_2 = compute_all_possible_arrangements(lines, 5)
 print(f"answer 2 is {answer_2}")