graph solution, still running

dreiundzwanzig.py

@@ -28,27 +28,6 @@ def solve(kart, pos, dist):
             nextpos = add(pos, d)
             q += [(newkart, nextpos, dist + 1), ]
 
-def solve2(kart, pos, dist):
-    #ic(pos, dist)
-    global best, q, longest100
-    if dist - dist % 100 > longest100:
-        longest100 = dist - dist % 100
-        ic(longest100)
-    if pos == fin:
-        if dist > best:
-            best = dist
-            ic(best)
-        return
-    if not (pos[0] >= 0 and pos[1] >= 0 and pos[0] < h and pos[1] < w):
-        return
-    if not kart[pos]:
-        return
-    newkart = kart.copy()
-    newkart[pos] = False
-    for d in DIRS:
-        nextpos = add(pos, d)
-        q += [(newkart, nextpos, dist + 1), ]
-
 kart = np.asarray([[c for c in l] for l in lines(open(0))])
 h, w = kart.shape
 beg, fin = [(i, np.argmax(kart[i] == '.')) for i in (0, h - 1)]
@@ -63,9 +42,51 @@ while q:
 
 print(best)
 
-q += [(kart != '#', beg, 0)]
+vertices = [beg, fin]
+edges = defaultdict(lambda: set())
 
+def find_vertices(kart, pos, dist, prev_vertex):
+    global vertices, edges, q
+    newkart = kart.copy()
+    newkart[pos] = False
+    newposes = []
+    for d in DIRS:
+        nextpos = add(pos, d)
+        if not (nextpos[0] >= 0 and nextpos[1] >= 0 and nextpos[0] < h and nextpos[1] < w):
+            continue
+        if not kart[nextpos]:
+            continue
+        newposes += [nextpos, ]
+    if len(newposes) > 1: # we're on a new(?) vertex
+        if pos not in vertices:
+            vertices += [pos, ]
+            for p in newposes:
+                q += [(newkart, p, 1, pos), ]
+        edges[prev_vertex] |= {(pos, dist)}
+        edges[pos] |= {(prev_vertex, dist)}
+    elif len(newposes) == 1:
+        q += [(newkart, newposes[0], dist + 1, prev_vertex), ]
+    elif pos == fin:
+        edges[prev_vertex] |= {(pos, dist)}
+        edges[pos] |= {(prev_vertex, dist)}
+
+def lengths(fro, edges, to):
+    if fro == to:
+        return [0, ]
+    acc = []
+    for e in edges[fro]:
+        newegg = deepcopy(edges)
+        newegg[e[0]].remove((fro, e[1]))
+        newegg[fro].remove(e)
+        for l in lengths(e[0], newegg, fin):
+            acc += [e[1] + l, ]
+    return acc
+
+q += [(kart != '#', beg, 0, beg), ]
 while q:
-    solve2(*q.pop())
+    find_vertices(*q.popleft())
+
+ic(edges)
+
+print(max(lengths(beg, edges, fin)))
 
-print(best)