Simplify day 10

2024/10_trails.py

@@ -2,23 +2,21 @@
 import sys
 from collections import Counter
 
-def trail_ends(grid, headx, heady):
-    h = len(grid)
-    w = len(grid[0])
-    work = [(headx, heady, 0, set())]
-    while work:
-        x, y, num, visited = work.pop()
-        if num == 9:
-            yield x, y
-        else:
-            for nb in ((x - 1, y), (x + 1, y), (x, y - 1), (x, y + 1)):
-                nx, ny = nb
-                if 0 <= nx < w and 0 <= ny < h and grid[ny][nx] == num + 1 \
-                        and nb not in visited:
-                    work.append((nx, ny, num + 1, visited | {nb}))
-
 grid = [list(map(int, line[:-1])) for line in sys.stdin]
-trails = [Counter(trail_ends(grid, x, y))
+w = len(grid[0])
+h = len(grid)
+
+def trail_ends(x, y, num, visited=set()):
+    if num == 9:
+        yield x, y
+    else:
+        for nb in ((x - 1, y), (x + 1, y), (x, y - 1), (x, y + 1)):
+            nx, ny = nb
+            if 0 <= nx < w and 0 <= ny < h and \
+                    grid[ny][nx] == num + 1 and nb not in visited:
+                yield from trail_ends(nx, ny, num + 1, visited | {nb})
+
+trails = [Counter(trail_ends(x, y, 0))
           for y, row in enumerate(grid)
           for x, num in enumerate(row)
           if num == 0]