Question

Add a public member function to the BST class below that returns the size of the tree—the number of the nodes in the tree. For simplicity, the class contains only the key and not a value. You may add any helper functions you find necessary. (Hint: think recursion)

template <typename T>

struct Node {

                T key;

                Node<T>*              left;

                Node<T>*              parent;

                Node<T>*              right;

};

template <typename T>

class BST {

private:

        Node<T>* root;

public:

        BST(): root(nullptr) { }

        int Size() {

                        //YOUR CODE GOES HERE

        }

       

};

Answer 1

template<typename T>
struct Node {
    T key;
    Node<T> *left;
    Node<T> *parent;
    Node<T> *right;
};

template<typename T>
class BST {
private:
    Node<T> *root;
    // recursive helper function
    int Size(Node<T> *node) {
        if (node != nullptr) {
            return 1 + Size(node->left) + Size(node->right);
        }
        return 0;
    }
public:
    BST() : root(nullptr) {}

    int Size() {
        return Size(root);  // call recursive helper
    }
};