This example shows how to pass a user-defined function as a parameter to the binary tree traversal algorithms. For illustration purposes, we show how to use only the inorder traversal function. The following program uses the class bSearchTreeType, which is derived from the class binaryTreeType, to build the binary tree. The traversal functions are included in the class binaryTreeType, which are then inherited by the class bSearchTreeType.

#include <iostream>

#include "binarySearchTree.h"

using namespace std;

void print(int& x);

void update(int& x);

int main()

{

bSearchTreeType<int> treeRoot; //Line 1

int num; //Line 2

cout << "Line 3: Enter numbers ending "

<< "with -999." << endl; //Line 3

cin >> num; //Line 4

while (num != -999) //Line 5

{

treeRoot.insert(num); //Line 6

cin >> num; //Line 7

}

cout << endl

<< "Line 8: Tree nodes in inorder: "; //Line 8

treeRoot.inorderTraversal(print); //Line 9

cout << endl << "Line 10: Tree Height: "

<< treeRoot.treeHeight()

<< endl << endl; //Line 10

cout << "Line 11: ******* Update Nodes "

<< "*******" << endl; //Line 11

treeRoot.inorderTraversal(update); //Line 12

cout << "Line 13: Tree nodes in inorder "

<< "after the update: " << endl

<< " "; //Line 13

treeRoot.inorderTraversal(print); //Line 14

cout << endl << "Line 15: Tree Height: "

<< treeRoot.treeHeight() << endl; //Line 15

return 0; //Line 16

}

void print(int& x) //Line 17

{

cout << x << " "; //Line 18

}

void update(int& x) //Line 19

{

x = 2 * x; //Line 20