minor 9b refactor

9/b.py

@@ -12,27 +12,28 @@ with open("input.txt") as f:
 
 
 width, height = x, y
-
-
 lows = []
+candidates = [(-1, 0), (1, 0), (0, -1), (0, 1)]
 
 
 for i, ((x, y), value) in enumerate(zone.items()):
-    if x > 0 and zone[(x-1, y)] <= value:
-        continue
-    if x < width-1 and zone[(x+1, y)] <= value:
-        continue
-    if y > 0 and zone[(x, y-1)] <= value:
-        continue
-    if y < height-1 and zone[(x, y+1)] <= value:
-        continue
-    lows.append((x, y, ))
+    ok = True
+    for c_x, c_y in candidates:
+        newx = x + c_x
+        newy = y + c_y
+        if newx < 0 or newx >= width or newy < 0 or newy >= height:
+            continue  # off map
+        newpoint = (newx, newy, )
+        if zone[newpoint] <= value:
+            ok = False
+            break
+    if ok:
+        lows.append((x, y, ))
 
 
 def find_basin(point, in_basin):
     # from the starting point, explore points around it recursing into each
     in_basin.update([point])
-    candidates = [(-1, 0), (1, 0), (0, -1), (0,1)]
     for c_x, c_y in candidates:
         newx = point[0] + c_x
         newy = point[1] + c_y