Binary Search Tree insert causing a stack overflow C++

Question

I am trying to insert values into a binary search tree. I have a class for the leaves of the tree, and a class for the collection itself. Here is the class for the leaves:

template <class K, class T>
class BSTLeaf{
public:
    BSTLeaf(const K& k, const T& c);
    K key;
    T data;
    BSTLeaf * left;
    BSTLeaf * right;
    void insert(const K& k, const T& c);
private:
};

Here is the insert function for the other class that is working as intended:

template <class K,class T>
void BSTKeyedCollection<K,T>::insert(const K& k, const T& c){
    if(root != NULL){
        cout << "trying to insert " << c << endl;
        root->insert(k,c);
    }
    else{
        cout << "ROOT WAS NULL" << endl;
        root = new BSTLeaf<K,T>(k,c);
        cout << "The root node contains " << c << endl;
    }
}

Here is the function that is causing the overflow:

template <class K, class T>
void BSTLeaf<K,T>::insert(const K& k, const T& c){
    //if the key is less than the node it comes to
    if(k < key){
        if(left == NULL){
            left = new BSTLeaf<K,T>(k,c);
        }
        else
            insert(k,c);
    }
    if(k > key){
        if(right == NULL){
            right = new BSTLeaf<K,T>(k,c);
        }
        else
            insert(k,c);
    }

}

Not sure if the constructor would be helpful but here it is:

template <class K,class T>
BSTLeaf<K,T>::BSTLeaf(const K& k, const T& c){
    key = k;
    data = c;
    left = NULL;
    right = NULL;
};

We are allowed to assume that K will always be a type that < and > will work for so that is not an issue. The function will insert a value at the root, insert one more value, and then overflow. Thanks in advance for the help!

Answer 1

You are calling the same function on the same instance you are in, causing a stack overflow (cyclical calls to the same function). I think you meant left->insert(k,c); and right->insert(k,c); .

Answer 2

Looks like your problem is coming from the recursive call to insert . You should call it on the right or left leaf of the current leaf:

template <class K, class T>
void BSTLeaf<K,T>::insert(const K& k, const T& c){
    //if the key is less than the node it comes to
    if(k < key){
        if(left == NULL){
            left = new BSTLeaf<K,T>(k,c);
        }
        else
            left->insert(k,c);
    }
    if(k > key){
        if(right == NULL){
            right = new BSTLeaf<K,T>(k,c);
        }
        else
            right->insert(k,c);
    }

}