day 18 part 2

day18/astar.py

@@ -28,8 +28,8 @@ def search(start, is_goal, neighbors, heuristic=None, worst=None):
         done[this] = (cost_so_far, prev)
 
         if is_goal(this):
-            print("astar: visited", len(done), "nodes")
-            print("astar: pending", len(q), "nodes")
+            #print("astar: visited", len(done), "nodes")
+            #print("astar: pending", len(q), "nodes")
             # reconsruct the path
             n = this
             path = []

day18/sol.py

@@ -7,41 +7,54 @@ def parse(file):
         for line in file
     ]
 
-def solve(file, N=70, T=1024):
+def solve(file, N=71, T=1024):
     falling = parse(file)
-
-    start = (0,0,0) # x,y,t
-
-    map = [[0]*N for _ in range(N)]
     inf = float('inf')
+    map = [[0]*N for _ in range(N)]
     map = defaultdict(lambda: inf)
-    for t,p in enumerate(falling):
-        map[p] = t
-    
-    def neighbors(n):
-        x,y,t = n
-        #if T < map[x,y]:
-            # can't move out of a blocked space
-        #    return []
-        def push(x,y,t):
-            if 0 <= x < N and 0 <= y < N:
-                if T <= map[x,y]:
-                    out.append((1,(x,y,t)))
-        out = []
-        push(x+1,y,t+1)
-        push(x,y+1,t+1)
-        push(x-1,y,t+1)
-        push(x,y-1,t+1)
-        return out
-
-    end = N-1, N-1
-    def isgoal(n):
-        x,y,_ = n
-        return (x,y) == end
-
-    sol = astar.search(start, isgoal, neighbors)
+    for i,p in enumerate(falling):
+        map[p] = i
+    sol = _solve(map, N, T)
     print(sol)
     print(len(sol[-1])-1)
 
+def _solve(map, N=71, T=1024):
+    start = (0,0) # x,y,t
+    
+    def neighbors(n):
+        x,y = n
+        def push(x,y):
+            if 0 <= x < N and 0 <= y < N:
+                if T <= map[x,y]:
+                    out.append((1,(x,y)))
+        out = []
+        push(x+1,y)
+        push(x,y+1)
+        push(x-1,y)
+        push(x,y-1)
+        return out
+
+    end = N-1, N-1
+
+    def heuristic(n):
+        return abs(end[0] - n[0]) + abs(end[1] - n[1])
+
+    return astar.search(start, end, neighbors, heuristic)
+
+import math
+def solve2(file, N=71, T=1024):
+    falling = parse(file)
+    inf = float('inf')
+    map = [[0]*N for _ in range(N)]
+    map = defaultdict(lambda: inf)
+    for i,p in enumerate(falling):
+        map[p] = i
+        sol = _solve(map, N, i+1)
+        if math.isinf(sol[0]):
+            print(p)
+            break
+
 solve(open("sample1.in"), N=7, T=12)
+solve2(open("sample1.in"), N=7, T=12)
 solve(open("input"), N=71, T=1024)
+solve2(open("input"), N=71, T=1024)