day 10 optimizations

- reduce duplicate queue entries by not appending to the queue if a
  point has a nonzero count. (if there's a count then it must have
  already been queued.)

- use the correct data structure for a double-ended queue so pop(0) has
  less work to do

- factor out the list of summits

of these three changes, only the last one has any noticable effect
on the run time. 🤷

day10/sol.py

@@ -1,5 +1,5 @@
 import itertools 
-from collections import Counter
+from collections import Counter, deque
 def read(file):
     return [line.strip() for line in file]
 
@@ -18,20 +18,22 @@ def solve(file):
         c = get(x,y)
         if c == h:
             assert (x,y) not in done
-            queue.append((x,y))
+            if (x,y) not in count:
+                queue.append((x,y))
             count[x,y] += n
 
     trailheads = [(x,y) for x,y in points() if get(x,y) == '0']
+    summits = [(x,y) for x,y in points() if get(x,y) == '9']
 
     t1 = 0
     t2 = 0
     for p in trailheads:
-        queue = [p]
+        queue = deque([p])
         done = set()
         count = Counter()
         count[p] = 1
         while queue:
-            x,y = queue.pop(0)
+            x,y = queue.popleft()
             #print(x,y,queue)
             if (x,y) in done:
                 continue
@@ -44,8 +46,8 @@ def solve(file):
                 visit(x-1,y,h,n)
                 visit(x,y+1,h,n)
                 visit(x,y-1,h,n)
-        for x,y in points():
+        for x,y in summits:
-            if get(x,y) == '9' and (x,y) in done:
+            if (x,y) in done:
                 t1 += 1
                 t2 += count[x,y]