The height of a binary tree is defined to be 0 for an empty tree, 1 for a tree consisting of a single node, 2 for a tree consisting of a root node with one or two children that are leaf nodes, etc.

Complete the definition of function height() below so it returns the height of the tree whose root is given as its argument. (Hint: recursion is your friend.)

// return the height of the binary search tree with node* head_ptr

int height(node* head_ptr)