KD树插入

Question

//inserts a node into the KD tree
void KDTree::insert(KDNode *point){
//If there is nothing to insert
if (point == NULL) return; 

//If the root points to nothing
if (root == NULL){
    root = point; 
    root->left = NULL; 
    root->right = NULL;
    return; 
}

insertKD(point, root); 
}

//helper function to facilitate recursion 
void KDTree::insertKD(KDNode *point, KDNode *r){
//If the point is already in the tree, don't store it
if (point->coordinates.getX() == r->coordinates.getX() && point->coordinates.getY() == r->coordinates.getY()){
    return;
} 

//save key value of parent
int key = r->key; 

//when the key is 0, we compare x-values
if (key == 0){
    //if the x-value of the point is less than the parent's store it at the left
    if (point->coordinates.getX() < r->coordinates.getX()){
        if (r->left == NULL){
            r->left = point;
            //set key to 1 since its parent has key 0
            point->key = 1; 
            return; 
        }
        else insertKD(point, r->left);
    }

    //if the x-value of the point is more than or equal the parent's store it at the right
    if (point->coordinates.getX() >= r->coordinates.getX()){
        if (r->right == NULL){
            r->right = point; 
            //set key to 1 since its parent has key 0
            point->key = 1; 
            return; 
        }
        else insertKD(point, r->right);
    }
}

//when the key is 1, we compare y-values 
if (key == 1){
    //if the y-value of the point is less than the parent's store it at the left
    if (point->coordinates.getY() < r->coordinates.getY()){
        if (r->left == NULL){
            r->left = point; 
            //set key to 0 since its parent has key 1
            point->key = 0;
            return; 
        }
        else insertKD(point, r->left);
    }

    //if the y-value of the point is more than or equal the parent's store it at the right
    if (point->coordinates.getY() >= r->coordinates.getY()){
        if (r->right == NULL){
            r->right = point; 
            //set key to 0 since its parent has key 1
            point->key = 0;
            return; 
        }
        else insertKD(point, r->right);
    }
}  
} 

当我测试树是否工作时，我意识到它没有正确插入元素（它只插入第一个）。我有一个for循环，为类类型分配内存，然后使用此函数。我进入调试模式，看看指针指向的位置。第一次（i = 0）我分配的新对象指向一个内存值（预期），然后在下一个循环（i = 1），root指向相同的内存值（也是预期的），但当我调用函数再次插入，在第三个循环中，root-＆gt; left或root-＆gt; right的值不指向任何东西（它只是说0x0，我的构造函数将它们初始化为NULL）。我手动完成的代码出了什么问题，它似乎在逻辑上有效？