21a

einundzwanzig.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python3
+
+from useful import *
+
+target = 64 if not len(sys.argv) > 1 else int(sys.argv[1])
+
+DIRS = (-1, 0), (1, 0), (0, -1), (0, 1)
+
+def add(a, b):
+    return tuple(map(lambda u, v: u + v, a, b))
+
+def cango(pos):
+    global w, h
+    return pos[0] >= 0 and pos[1] >= 0 and pos[0] < h and pos[1] < w and \
+            kart[pos] != '#'
+
+def solve(kart, pos, dist):
+    global dmap, target, q
+    if dist > target:
+        return
+    if dist >= dmap[pos]:
+        return
+    dmap[pos] = dist
+    for d in DIRS:
+        nextpos = add(pos, d)
+        if cango(nextpos):
+            q += [(kart, nextpos, dist + 1), ]
+
+kart = np.asarray([[c for c in l] for l in lines(open(0))])
+h, w = kart.shape
+dmap = np.ones((h, w), dtype=int) * 666
+beg = next(zip(*np.where(kart == 'S')))
+q = deque()
+
+q += [(kart, beg, 0)]
+
+while q:
+    solve(*q.popleft())
+
+print(np.sum(np.vectorize(lambda x: x <= target and x % 2 == 0)(dmap)))

test21

@@ -0,0 +1,11 @@
+...........
+.....###.#.
+.###.##..#.
+..#.#...#..
+....#.#....
+.##..S####.
+.##..#...#.
+.......##..
+.##.#.####.
+.##..##.##.
+...........