day 10, simple grid walk, refactor into lib

d10/run.py

@@ -0,0 +1,23 @@
+import sys
+from grid import *
+
+L = sys.stdin.read().strip().split("\n")
+G = [list(map(int,l)) for l in L]
+
+def walk(grid, x, y, p=-1):
+    v = get_in_grid(G, x, y)
+    if v is None or v != p + 1: # wrong way
+        return
+    if v == 9:  # end of trail
+        yield (x, y)
+    for dx, dy in MOVE4:
+        yield from walk(grid, x+dx, y+dy, p+1)
+
+U = R = 0
+for (x0,y0) in ((x,y) for y,row in enumerate(G) for x,v in enumerate(row) if v == 0):
+    s = set()
+    for ends in walk(G, x0, y0):
+        s.add(ends)
+        R += 1
+    U += len(s)
+print(U, R)