Solve 2023:12 "Hot Springs"

2023-python/output/day_12.py

@@ -0,0 +1,64 @@
+from functools import cache
+from output import answer
+
+n = 12
+title = "Hot Springs"
+
+
+@answer(1, "sum of all possible combinations is {}")
+def part_1(presolved):
+    return presolved[0]
+
+
+@answer(2, "sum of all possible combinations is {} when unfolded")
+def part_2(presolved):
+    return presolved[1]
+
+
+def presolve(data):
+    lines = [
+        (a, list(map(int, b.split(","))))
+        for a, b in (line.split() for line in data.splitlines())
+    ]
+    p1 = sum(_inspect(a, tuple(b)) for a, b in lines)
+    p2 = sum(_inspect("?".join([a] * 5), tuple(b * 5)) for a, b in lines)
+    return p1, p2
+
+
+@cache
+def _inspect(s, cs):
+    r = len(s)
+    csl = len(cs)
+    if r == 0:
+        return 1 if csl == 0 else 0
+    o, *f = s
+    f = "".join(f)
+    if o == ".":
+        return _inspect(f, cs)
+    if o == "?":
+        return _inspect("." + f, cs) + _inspect("#" + f, cs)
+    if not csl:
+        return 0
+    g = cs[0]
+    if g > r or "." in s[0:g]:
+        return 0
+    elif csl > 1:
+        if g + 1 > r or s[g] == "#":
+            return 0
+        else:
+            return _inspect(s[g + 1 :], cs[1:])
+    elif csl == 1:
+        return _inspect(s[g:], ())
+
+
+if __name__ == "__main__":
+    with open("./input/12.txt", "r") as f:
+        inp = f.read().strip()
+
+    inp = presolve(inp)
+
+    a = part_1(inp)
+    b = part_2(inp)
+
+    assert a == 7118
+    assert b == 7030194981795