Unreal Engine implements priority queue (priority_queue)

brief description

Priority queue is implemented using heap sort. The access method depends on the heapsort method.
There is a heap sorting method in TArray, which can easily realize the heap sorting of TArray type.

Heapify: initialize the heap
HeapPush: push elements to the heap
HeapPop: pop the top element of the heap

	TArray<int32> openSet;
	for (int32 i=0;i<10;i++)
	{
    
    
		openSet.Emplace(UKismetMathLibrary::RandomInteger(100));
	}
	FString logText = "";
	for (int32 i=0;i<openSet.Num();i++)
	{
    
    
		logText.Append(FString::FromInt(openSet[i]));
		logText.Append(" ");
	}
	UE_LOG(LogTemp, Warning, TEXT("===logText	%s"),*logText);

	openSet.Heapify();

	logText = "";
	for (int32 i = 0; i < openSet.Num(); i++)
	{
    
    
		logText.Append(FString::FromInt(openSet[i]));
		logText.Append(" ");
	}
	UE_LOG(LogTemp, Warning, TEXT("===logText Heapify	%s"), *logText);

	openSet.HeapPush(50);
	openSet.HeapPush(50);
	openSet.HeapPush(50);
	openSet.HeapPush(60);
	logText = "";
	for (int32 i = 0; i < openSet.Num(); i++)
	{
    
    
		logText.Append(FString::FromInt(openSet[i]));
		logText.Append(" ");
	}
	UE_LOG(LogTemp, Warning, TEXT("===logText HeapPush	%s"), *logText);

	logText = "";
	while (openSet.Num()>0)
	{
    
    
		int32 _i = 0;
		openSet.HeapPop(_i);
		logText.Append(FString::FromInt( _i));
		logText.Append(" ");
	}
	UE_LOG(LogTemp, Warning, TEXT("===logText HeapPop	%s"), *logText);

In practical applications, it is often not a simple int push sort, there will be more complex requirements, and a more customized heap sort method needs to be implemented to realize the priority queue.

References

UE4's TArray (3)
UE – Priority Queue priority queue

demo

First, you need to write two Structs, one is the element of TArray, and the other is sorted by heap

//TArray的元素
struct TNode
{
    
    
	TNode() {
    
    };
	TNode(FString _key, int32 _prority) :key(_key), prority(_prority) {
    
    };
	int32 prority;
	FString key;

};
//TArray的堆排序规则
struct TNodeLess
{
    
    
	FORCEINLINE bool operator()(const TNode& A, const TNode& B) const
	{
    
    
		return A.prority < B.prority;
	}
};

test code

//创建一个TNode的数组，并往数组里添加元素
	TArray<TNode> openSet;
	for (int32 i = 0; i < 10; i++)
	{
    
    
		TNode n(FString::FromInt(i), UKismetMathLibrary::RandomInteger(100));//随机添加优先级
		openSet.Emplace(n);
	}
	//打印原始数组
	FString logText = "";
	for (int32 i = 0; i < openSet.Num(); i++)
	{
    
    
		logText.Append(openSet[i].key);
		logText.Append("-");
		logText.Append(FString::FromInt(openSet[i].prority));
		logText.Append(" ");
	}
	UE_LOG(LogTemp, Warning, TEXT("===logText 	%s"), *logText);
	
	//将数组按照排序规则进行堆排序
	openSet.Heapify(TNodeLess());
	//打印堆排序之后的元素
	logText = "";
	for (int32 i = 0; i < openSet.Num(); i++)
	{
    
    
		logText.Append(openSet[i].key);
		logText.Append("-");
		logText.Append(FString::FromInt(openSet[i].prority));
		logText.Append(" ");
	}
	UE_LOG(LogTemp, Warning, TEXT("===logText Heapify	%s"), *logText);

	//往数组里堆排序规则添加元素
	TNode n1("n1", 50);
	TNode n2("n2", 60);
	TNode n3("n3", 70);
	openSet.HeapPush(n1,TNodeLess());
	openSet.HeapPush(n2, TNodeLess());
	openSet.HeapPush(n3, TNodeLess());
	//打印添加新元素之后的数组
	logText = "";
	while (openSet.Num() > 0)
	{
    
    
		TNode n;
		openSet.HeapPop(n, TNodeLess());//弹出最优先元素
		logText.Append(n.key);
		logText.Append("-");
		logText.Append(FString::FromInt(n.prority));
		logText.Append(" ");
	}
	UE_LOG(LogTemp, Warning, TEXT("===logText HeapPop	%s"), *logText);