C中的四叉树实现:异常抛出读访问冲突

Question

我试图在C语言中实现一个四叉树，但是我有一个读访问冲突，我花了几个小时试图弄清楚。请注意，我已将所有成员变量公开，仅用于调试工作。

每当我试图细分一个象限，即根象限，我得到

抛出异常：读取访问冲突。标准：：_Vector_alloc

四叉树由一个指向连续象限数组的指针和点组成。这些指针被传递到每一个象限，所以它们能够写入而不需要复制。

我做错了什么？你能提出改进的建议吗？

这是我的四叉树类：

  class Quadtree
{
private:

    Boundary rootBoundary;
public:
    std::vector<Ball>* dataPtr = nullptr;
    std::vector<Quadrant>* quadrantPtr = nullptr;
    Quadtree(const Boundary& b);


};

    Quadtree::Quadtree(const Boundary& bo)
    :rootBoundary(bo)
{
    std::vector<Ball>* bPtr = new std::vector<Ball>;
    std::vector<Quadrant>* qPtr = new std::vector<Quadrant>;
    quadrantPtr = qPtr;
    dataPtr = bPtr;


    Quadrant Root(bo, quadrantPtr, dataPtr);

}

四叉树包含所有象限以及数据存储。

这是象限类：

 class Quadrant
    {
    private:

    public:
        std::vector<Quadrant>* quadrantPtr = nullptr;
        std::vector<Ball>* dataPtr = nullptr;
        Boundary m_boundary;
        std::vector<unsigned int> elementIndex;
        int first_child_index = -1;
        int count = 0;

        Quadrant(Boundary b, std::vector<Quadrant>* qPtr, std::vector<Ball>* dPtr);
        void Subdivide();
        bool Insert(Ball* Ball);
        void Display(sf::RenderWindow& myWindow);

    };


Quadrant::Quadrant(Boundary b, std::vector<Quadrant>* qPtr, std::vector<Ball>* bPtr)
    :dataPtr(bPtr), quadrantPtr(qPtr), m_boundary(b)
{
    qPtr->push_back(*this);
}
void Quadrant::Subdivide()
{
    float cx = m_boundary.m_Centre.x;
    float cy = m_boundary.m_Centre.y;
    float qw = m_boundary.m_halfSize.x / 2;
    float qh = m_boundary.m_halfSize.y / 2;

    sf::Vector2f halfSize{ qw, qh };
    first_child_index = quadrantPtr->size();

    Boundary NE(sf::Vector2f{ cx + qw, cy - qh }, halfSize);
    Quadrant NEQ(NE, quadrantPtr, dataPtr);
    Boundary NW(sf::Vector2f{ cx - qw, cy - qh }, halfSize);
    Quadrant NWQ(NW, quadrantPtr, dataPtr);
    Boundary SE(sf::Vector2f{ cx + qw, cy + qh }, halfSize);
    Quadrant SEQ(SE, quadrantPtr, dataPtr);
    Boundary SW(sf::Vector2f{ cx - qw, cy + qh }, halfSize);
    Quadrant SWQ(SW, quadrantPtr, dataPtr);


}

bool Quadrant::Insert(Ball* ball)
{
    if (!m_boundary.ContainsPoint(*ball))
    {
        return false;
    }
    if (count < 4)
    {
        elementIndex.push_back(dataPtr->size());
        count++;
        return true;
    }
    else
    {
        if (first_child_index == -1)
        {
            std::cout << "subdividing" << std::endl;
            Subdivide();
        }
        for (int i = 0; i < 4; i++)
        {
            if (quadrantPtr->at(first_child_index + i).Insert(ball))
            {
                return true;
            }
        }
    }

}

void Quadrant::Display(sf::RenderWindow& myWindow)
{
    myWindow.draw(m_boundary.boundary);
    if (first_child_index != -1)
    {
        for (int i = 0; i < 4; i++)
        {
            quadrantPtr->at(first_child_index + i).Display(myWindow);
        }
    }
}

以下是表示象限AABB的边界类：

class Boundary
{
private:

public:
    sf::Vector2f m_Centre;
    sf::Vector2f m_halfSize;
    sf::RectangleShape boundary;
    Boundary();
    Boundary(const sf::Vector2f& centre, const sf::Vector2f& halfSize);
    bool ContainsPoint(const Ball& ball) const;
    ~Boundary();

};

Boundary::Boundary()
{

}
Boundary::Boundary(const sf::Vector2f& Centre, const sf::Vector2f& HalfSize)
    :m_Centre(Centre), m_halfSize(HalfSize)
{
    boundary.setSize(m_halfSize + m_halfSize);
    boundary.setOrigin(m_halfSize);
    boundary.setPosition(m_Centre);
    boundary.setFillColor(sf::Color::Transparent);
    boundary.setOutlineColor(sf::Color::White);
    boundary.setOutlineThickness(2);
}
bool Boundary::ContainsPoint(const Ball& ball) const
{
    bool contains = false;
    if (ball.ball.position.x > m_Centre.x - m_halfSize.x && ball.ball.position.x < m_Centre.x + m_halfSize.x)
    {
        if (ball.ball.position.y > m_Centre.y - m_halfSize.y && ball.ball.position.y < m_Centre.y + m_halfSize.y)
        {
            contains = true;
        }
    }
    return contains;
}

Answer 1

您的< code>Root对于构造函数来说是本地的。也就是说，它在< code>Quadtree构造结束时被销毁。改为使其成为类成员。

你也不需要用< code>new来创建向量，它们本身就是指针。使它们也成为类成员，并使用< code >

注意：成员顺序很重要，它是它们初始化的顺序。