Pathfinding: Added optimization for Dijkstra

Piratmac · Piratmac · commit dd568b50f526 · 2020-08-22T16:34:53.000+02:00
diff --git a/2019/pathfinding.py b/2019/pathfinding.py
@@ -162,7 +162,10 @@ def add_walls(self, vertices):
         for vertex in vertices:
             if vertex in self.edges:
                 del self.edges[vertex]
-                self.vertices.remove(vertex)
+                if isinstance(self.vertices, list):
+                    self.vertices.remove(vertex)
+                else:
+                    del self.vertices[vertex]
                 changed = True
 
         self.edges = {
@@ -489,6 +492,7 @@ def dijkstra(self, start, end=None):
         heapq.heapify(frontier)
         self.distance_from_start = {start: 0}
         self.came_from = {start: None}
+        min_distance = float("inf")
 
         while frontier:
             current_distance, vertex = heapq.heappop(frontier)
@@ -497,6 +501,10 @@ def dijkstra(self, start, end=None):
             if not neighbors:
                 continue
 
+            # No need to explore neighbors if we already found a shorter path to the end
+            if current_distance > min_distance:
+                continue
+
             for neighbor, weight in neighbors.items():
                 # We've already checked that node, and it's not better now
                 if neighbor in self.distance_from_start and self.distance_from_start[
@@ -511,6 +519,9 @@ def dijkstra(self, start, end=None):
                 self.distance_from_start[neighbor] = current_distance + weight
                 self.came_from[neighbor] = vertex
 
+                if neighbor == end:
+                    min_distance = min(min_distance, current_distance + weight)
+
         return end is None or end in self.distance_from_start
 
     def a_star_search(self, start, end=None):
