Tree building function from precalculated tree

Question

I am building a binary tree. The binary tree is pre-built in a file and I need to construct it. Due to the way it is structured, I read the tree into an array. Each tree nodes look something like this.

struct Tree_Node
{
    float normalX;
    float normalY;
    float normalZ;
    float splitdistance;
    long region;
    long left, right; //array index
    Tree_Node* left_node; // pointer to left node
    Tree_Node* right_node; // pointer to right node
} typedef Tree_Node;

I have tried a number of ways to write some code that will build the tree. Let me give you some pseudocode so you understand what I am trying to do.

• Read in head node. Node is number one in the array.
• If the node has a right and left array index, create new nodes and insert the information from the array indicies into that tree node.
• If the node does not have a right and left index, it is a leaf node.

Here is my building function:

void WLD::treeInsert(BSP_Node *tree_root, int node_number)
{
    /// Add the item to the binary sort tree to which the parameter
    // "root" refers.  Note that root is passed by reference since
    // its value can change in the case where the tree is empty.
    if ( tree_root == NULL ) 
    {
        // The tree is empty.  Set root to point to a new node containing
        // the new item.  This becomes the only node in the tree.
        tree_root = new BSP_Node();

        tree_root->normalX = bsp_array[node_number].normal[0];
        tree_root->normalY = bsp_array[node_number].normal[1];
        tree_root->normalZ = bsp_array[node_number].normal[2];
        tree_root->splitdistance = bsp_array[node_number].splitdistance;;
        tree_root->region = bsp_array[node_number].region;
        tree_root->left = bsp_array[node_number].left;
        tree_root->right = bsp_array[node_number].right;
        tree_root->left_node[node_number];
        tree_root->right_node[node_number];

        errorLog.OutputSuccess("Inserting new root node: %i", node_number);
                    // NOTE:  The left and right subtrees of root
                    // are automatically set to NULL by the constructor.
                    // This is important...
    }

    if ( tree_root->left != 0 ) 
    {
        errorLog.OutputSuccess("Inserting left node number: %i!", tree_root->left);
        treeInsert( tree_root->left_node, tree_root->left );
    }
    else if (  tree_root->right != 0 )
    {
        errorLog.OutputSuccess("Inserting right node: %i!", tree_root->right);
        treeInsert( tree_root->right_node, tree_root->right );
    }
    else if ( tree_root->right == 0 && tree_root->left == 0)
    {
        errorLog.OutputSuccess("Reached a leaf node!");
        return;
    }
    else
    {
    errorLog.OutputError("Unknown BSP tree error!");
    }

}

My debug shows that the function tries to insert node 2 until the program crashes.

Can someone help me with this?

Answer 1

tree_root->left_node[node_number];

I don't see any code that initializes this array, so this'll be referring to something invalid.

Then by the time you come around to the next function

treeInsert( tree_root->left_node, tree_root->left );

treeInsert will be called with an invalid pointer, since left_node doesn't go anywhere.

I imagine you need something like tree_root->left_node = NULL instead of tree_root->left_node[node_number] so that the recursive call to treeInsert creates the next node.