Segmentation Fault in Binary Tree

Question

I'm getting a segmentation fault on my program when I try to insert to a binary search tree. Here's the declaration of the node:

template < class T > class binTreeNode {
friend class binTree < T >;
friend class binSTree < T >;
public:
    // default constructor
    binTreeNode ( const T& newData =T( ), binTreeNode < T >* newLeft = 0, binTreeNode < T >* newRight = 0 ) {
        data = newData;
        left = newLeft;
        right = newRight;
    }
private:
    T data; // data value in node
    binTreeNode < T > *left, *right; // links to other nodes
};

The functions below are all new, everything else (like height functions and constructors) are all done in the parent class, and shouldn't really be relevant. The new functions are:

template <class T>
class binSTree : public binTree<T> {
public:
    void insert (const T& newData) {
        if (root == NULL) {
            root = new binTreeNode<T>(newData);
        }
        else
            insert(root,newData);
    }
    bool search (const T& x) const {
        if (root != NULL)
            return search(root,x);
        else
            return false;
    }
    bool remove (const T& x) {
        if (root == NULL)
            return false;
        remove(root,x);
        return true;
    }
protected:
    binTreeNode<T>* root;
private:
    void insert (binTreeNode<T>*& ptr, const T& x) {
        if (ptr == NULL) {      // Base case, actual insertion
            binTreeNode<T>* newNode;
            newNode = new binTreeNode<T>(x);
            ptr = newNode;
            return;
        }
        if (x == ptr->data)
            return;
        else if (x < ptr->data)
            insert(ptr->left,x);
        else
            insert(ptr->right,x);
        return;
    }
    bool search (binTreeNode<T>* ptr, const T& x) const {
        if (ptr->data == x)
            return true;
        else if (x < ptr->data && ptr->left != NULL)
            search(ptr->left,x);
        else if (ptr->right != NULL)
            search(ptr->right,x);
        else
            return false;
    }
    binTreeNode<T>* remove (binTreeNode<T>* ptr, const T& x) {
        if (ptr == NULL)
            return NULL;
        else if (ptr->data == x && leaf(ptr)) {
            delete ptr;
            ptr = NULL;
            return ptr;
        }
        else if (ptr->data == x && !leaf(ptr))
            return ptr;
        else if (x < ptr->data) {
            ptr->left = remove(ptr->left,x);
            return ptr;
        }
        else {
            ptr->right = remove(ptr->right,x);
            return ptr;
        }
    }
    bool leaf (binTreeNode<T>* node) const {
        if (node->left != NULL || node->right != NULL)
            return false;
        return true;
    }
};

The segmentation fault, according to valgrind, is in the private insert in the conditional where I check if (x == ptr->data). Does anyone have any idea why this is? I've completely hit a wall. Thanks :3

Answer 1

There is a problem in your remove code that may or may not be the cause of your crash, but should definitely be fixed: when you recursively remove ptr->left or ptr->right that results in deleting the node, you should also set the left or right pointer in the parent to NULL; otherwise you open up your code to errors associated with dangling pointers.