Fix: O(N^2) cost of Station::RecomputeCatchmentForAll

Station::RemoveFromAllNearbyLists does not need to be called when
all station nearby lists have been cleared and are being regenerated.

src/station.cpp

@@ -455,11 +455,12 @@ bool Station::CatchmentCoversTown(TownID t) const
 /**
  * Recompute tiles covered in our catchment area.
  * This will additionally recompute nearby towns and industries.
+ * @param no_clear_nearby_lists If Station::RemoveFromAllNearbyLists does not need to be called.
  */
-void Station::RecomputeCatchment()
+void Station::RecomputeCatchment(bool no_clear_nearby_lists)
 {
 	this->industries_near.clear();
-	this->RemoveFromAllNearbyLists();
+	if (!no_clear_nearby_lists) this->RemoveFromAllNearbyLists();
 
 	if (this->rect.IsEmpty()) {
 		this->catchment_tiles.Reset();
@@ -526,7 +527,9 @@ void Station::RecomputeCatchment()
  */
 /* static */ void Station::RecomputeCatchmentForAll()
 {
-	for (Station *st : Station::Iterate()) { st->RecomputeCatchment(); }
+	for (Town *t : Town::Iterate()) { t->stations_near.clear(); }
+	for (Industry *i : Industry::Iterate()) { i->stations_near.clear(); }
+	for (Station *st : Station::Iterate()) { st->RecomputeCatchment(true); }
 }
 
 /************************************************************************/

src/station_base.h

@@ -501,7 +501,7 @@ public:
 
 	uint GetPlatformLength(TileIndex tile, DiagDirection dir) const override;
 	uint GetPlatformLength(TileIndex tile) const override;
-	void RecomputeCatchment();
+	void RecomputeCatchment(bool no_clear_nearby_lists = false);
 	static void RecomputeCatchmentForAll();
 
 	uint GetCatchmentRadius() const;