pathfinding now working for distance 2 or less

AdventureMap.cpp

@@ -7,6 +7,7 @@
 #include "AdventureCharacter.h"
 #include "Kismet/GameplayStatics.h"
 #include "Algo/Reverse.h"
+#include <unordered_map>
 
 // Sets default values
 AAdventureMap::AAdventureMap()
@@ -17,7 +18,7 @@ AAdventureMap::AAdventureMap()
 void AAdventureMap::BeginPlay()
 {
 	Super::BeginPlay();
-	UWorld* World = GetWorld();
+	World = GetWorld();
 	if (IsValid(BaseTileClass)) 
 	{ 
 		MakeGrid();
@@ -27,7 +28,6 @@ void AAdventureMap::BeginPlay()
 // Called once on Begin Play
 void AAdventureMap::MakeGrid() 
 {	
-	UWorld* World = GetWorld();
 	FVector NextHexAt = FVector();
 	float HexWidth = sqrt(3) * TileSize;
 	int QOffset = 0;
@@ -112,20 +112,94 @@ TArray<AHexTile*> AAdventureMap::Neighbors(AHexTile* OfHex)
 	return Neighbors;
 }
 
-// Be aware that the respective character will become relevant to this function at some point
+// Massive memory leak when Goal is more than 2 distance away from Start (leading to the Editor freezing)
+// Also freezes when the Goal is on the Edge of the map (i.e. has only 3 Neighbors)
 TArray<AHexTile*> AAdventureMap::FindPathAStar(AHexTile* Start, AHexTile* Goal)
 {
-	TArray<AHexTile*> Priorities;
-	Priorities.Init(Start, 1);
+	TArray<AHexTile*> PQ; // Makeshift Priority Queue.	(High value = Low priority)
+	PQ.Init(Start, 1);
 
-	// Editing Hex->CameFrom pointers, i.e. chaining Hexes
-	while (!Priorities.IsEmpty())
+	// The goal of this loop is to edit the Hex->CameFrom pointers, So as to chain Hexes from Goal to Start
+	while (!PQ.IsEmpty())
 	{
-		AHexTile* Current = Priorities[0];
-		Priorities.RemoveAt(0);
-		if (*Current == *Goal) 
+		AHexTile* Current = PQ[0];
+		PQ.RemoveAt(0);
+		UE_LOG(LogTemp, Warning, TEXT("Popping top priority Hex Q:%d|R:%d"), Current->Q, Current->R);
+
+		if (Current == Goal) // early exit
 		{ 
-			// UE_LOG(LogTemp, Warning, TEXT("Goal found!")); // debug
+			UE_LOG(LogTemp, Warning, TEXT("Goal found!!!")); // debug
+			break; 
+		}
+
+		UE_LOG(LogTemp, Warning, TEXT("Expanding the frontier...")); // debug
+		for (AHexTile* Next : Neighbors(Current))
+		{
+			int32 NewCost = Current->CostSoFar + Next->MoveCost;			
+			if (NewCost < Next->CostSoFar || !PQ.Contains(Next))
+			{
+				Next->CostSoFar = NewCost;
+				Next->CameFrom = Current;
+				PQ.Remove(Next);
+				int32 NewPrio = NewCost + Next->Distance(Goal); // Higher value = Lower priority
+
+				UE_LOG(LogTemp, Warning, TEXT("Hex Q:%d|R:%d pathing updated. Readjusting priorities..."), Next->Q, Next->R); // debug
+				if (!PQ.IsEmpty())
+				{
+					int32 OldPrio;
+					int32 OldIndex = PQ.Num() - 1; // To be inserted as lowest priority by default
+
+					for (AHexTile* Hex : PQ)
+					{
+						OldPrio = Hex->CostSoFar + Hex->Distance(Goal);
+						if (NewPrio <= OldPrio) // looking for 1. Hex in "PQ" with a lower priority than that of "Next"
+						{
+							PQ.Find(Hex, OldIndex); // redefining of "OldIndex"
+							break;
+						}
+					}
+					UE_LOG(LogTemp, Warning, TEXT("Inserting Hex at priority %d"), OldIndex); // debug
+					PQ.Insert(Next, OldIndex);
+				}
+				else
+				{
+					PQ.Add(Next);
+					UE_LOG(LogTemp, Warning, TEXT("Adding one last Candidate.")); // debug
+				}
+			}
+		}	
+	}
+	TArray<AHexTile*> Path;
+	AHexTile* Hex = Goal;
+	while (Hex != Start)
+	{
+		Path.Emplace(Hex);
+		Hex = Hex->CameFrom;
+	}
+	Algo::Reverse(Path);
+	return Path;
+}
+
+/*
+// alternative implementation using faster built in priority queue data structure
+TArray<AHexTile*> AAdventureMap::FindPathAStarPQ(AHexTile* Start, AHexTile* Goal)
+{
+	// TArray<AHexTile*> PQ;
+	std::priority_queue<AHexTile*, std::vector<AHexTile*>> PQ; // currently missing a custom comparator as third template arg (designating effective priority of pq elements)
+	std::unordered_map<AHexTile*, AHexTile*> CameFrom; // if in doubt: switch to templates instead of predefined hex types
+	// PQ.Init(Start, 1);
+	PQ.push(Start);
+	CameFrom[Start] = Start;
+
+	// while (!PQ.IsEmpty())
+	while (!PQ.empty())
+	{
+		AHexTile* Current = PQ.top();
+		// PQ.RemoveAt(0);
+		PQ.pop();
+		if (Current == Goal)
+		{
+			UE_LOG(LogTemp, Warning, TEXT("Goal found!")); // debug
 			break;
 		}
 
@@ -133,56 +207,48 @@ TArray<AHexTile*> AAdventureMap::FindPathAStar(AHexTile* Start, AHexTile* Goal)
 		for (AHexTile* Next : Neighbors(Current))
 		{
 			int32 NewCost = Current->CostSoFar + Next->MoveCost;
-			
 			// UE_LOG(LogTemp, Warning, TEXT("Cost calculated.")); // debug
 
-			if (!Priorities.Contains(Next) || NewCost < Next->CostSoFar)
+			if (!PQ.Contains(Next) || NewCost < Next->CostSoFar)
 			{
 				// UE_LOG(LogTemp, Warning, TEXT("New candidate found.")); // debug
-
 				Next->CostSoFar = NewCost;
 				int32 NewPrio = NewCost + Next->Distance(Goal);
 
 				// Adjust the Priority Queue
-				if (Priorities.Contains(Next)) { Priorities.Remove(Next); }
-				for (AHexTile* Hex : Priorities) // at this point Priorities is empty, need to make sure it's not.
+				if (PQ.Contains(Next)) { PQ.Remove(Next); }
+				for (AHexTile* Hex : PQ) // at this point PQ is empty, need to make sure it's not.
 				{
 					int32 OldPrio = Hex->CostSoFar + Hex->Distance(Goal);
 					int32 Index;
-					Priorities.Find(Hex, Index);
-
+					PQ.Find(Hex, Index);
 					// UE_LOG(LogTemp, Warning, TEXT("Comparing priorities...")); // debug
 
 					if (OldPrio > NewPrio)
 					{
-						Priorities.Insert(Next, Index);
+						PQ.Insert(Next, Index);
 						Next->CameFrom = Current;
-
 						// UE_LOG(LogTemp, Warning, TEXT("Looks promising!")); // debug
-
 						break;
 					}
-					if (Index == Priorities.Num() - 1 && OldPrio <= NewPrio)
+
+					if (Index == PQ.Num() - 1 && OldPrio <= NewPrio)
 					{
-						Priorities.Emplace(Next);
+						PQ.Emplace(Next);
 						Next->CameFrom = Current;
-
 						// UE_LOG(LogTemp, Warning, TEXT("Low prio added")); // debug
-
 						break;
 					}
 				}
-				if (Priorities.IsEmpty())
-				{
-					Priorities.Emplace(Next);
-				}
+
+				if (PQ.IsEmpty()) { PQ.Emplace(Next); }
 			}
 		}
 	}
 
 	TArray<AHexTile*> Path;
 	AHexTile* Hex = Goal;
-	while (*Hex != *Start)
+	while (Hex != Start)
 	{
 		Path.Emplace(Hex);
 		Hex = Hex->CameFrom;
@@ -191,3 +257,4 @@ TArray<AHexTile*> AAdventureMap::FindPathAStar(AHexTile* Start, AHexTile* Goal)
 	Algo::Reverse(Path);
 	return Path;
 }
+*/

AdventureMap.h

@@ -26,6 +26,8 @@ public:
 		int32 GridSize = 100; // squared is the number of Tiles
 	UPROPERTY(EditDefaultsOnly, BlueprintReadOnly, Category = "Config")
 		int32 TileSize = 100;
+	UPROPERTY()
+		UWorld* World;
 
 	UFUNCTION(BlueprintCallable, Category = "Generation")
 		void MakeGrid();
@@ -42,6 +44,8 @@ public:
 		TArray<AHexTile*> Neighbors(AHexTile* OfHex);
 	UFUNCTION(BlueprintCallable, Category = "Runtime")
 		TArray<AHexTile*> FindPathAStar(AHexTile* Start, AHexTile* Goal);
+	//UFUNCTION(BlueprintCallable, Category = "Runtime")
+	//	TArray<AHexTile*> FindPathAStarPQ(AHexTile* Start, AHexTile* Goal);
 
 	// Player spawn section
 	UPROPERTY(VisibleAnywhere, BlueprintReadWrite)

AdventurePlayerController.cpp

@@ -26,7 +26,7 @@ void AAdventurePlayerController::SetupInputComponent()
     Super::SetupInputComponent();
 
     // This is initialized on startup, you can go straight to binding
-    InputComponent->BindAction("LeftClick", IE_Pressed, this, &AAdventurePlayerController::AdvClick);
+    // InputComponent->BindAction("LeftClick", IE_Pressed, this, &AAdventurePlayerController::AdvClick);
 }
 
 void AAdventurePlayerController::AdvClick()
@@ -37,7 +37,7 @@ void AAdventurePlayerController::AdvClick()
     if (IsValid(Hit.GetActor()))
     {
         AHexTile* HitHex = (AHexTile*)Hit.GetActor();
-        // MapRef->FindPathAStar(CurrentHex, HitHex);   // this would currently cause a crash...
-        UE_LOG(LogTemp, Warning, TEXT("%d"), HitHex->Index);
+        MapRef->FindPathAStar(CurrentHex, HitHex);
+        // UE_LOG(LogTemp, Warning, TEXT("%d"), HitHex->Index);
     }
 }