preorder without recursion
void iterativePreorder(node *root)
{
// Base Case
if (root == NULL)
return;
// Create an empty stack and push root to it
stack<node *> nodeStack;
nodeStack.push(root);
while (nodeStack.empty() == false)
{
// Pop the top item from stack and print it
struct node *node = nodeStack.top();
printf ("%d ", node->data);
nodeStack.pop();
// Push right and left children of the popped node to stack
if (node->right)
nodeStack.push(node->right);
if (node->left)
nodeStack.push(node->left);
}
}