Data Structure Binary Tree: Print ancestors of a given binary tree node without recursion

http://www.geeksforgeeks.org/print-ancestors-of-a-given-binary-tree-node-without-recursion/

 #include <iostream>
 #include <vector>
 #include <algorithm>
 #include <queue>
 #include <stack>
 #include <string>
 #include <fstream>
 #include <map>
 using namespace std;

 struct node {
     int data;
     struct node *left, *right;
     node() : data(), left(NULL), right(NULL) { }
     node(int d) : data(d), left(NULL), right(NULL) { }
 };

 void printancestor(node *root, int key) {
     if (!root) return;
     stack<node*> S;
     while () {
         while (root && root->data != key) {
             S.push(root);
             root = root->left;
         }
         if (root && root->data == key) break;
         if (S.top()->right == NULL) {
             root = S.top();
             S.pop();
             while (!S.empty() && S.top()->right == root) {
                 root = S.top();
                 S.pop();
             }
         }
         root = S.empty()? NULL : S.top()->right;
     }
     while (!S.empty()) {
         cout << S.top()->data << " ";
         S.pop();
     }
 }

 int main() {
     node *root = new node();
     root->left = new node();
     root->right = new node();
     root->left->left = new node();
     root->left->right = new node();
     root->right->left = new node();
     root->right->right = new node();
     root->left->left->left = new node();
     root->left->right->right = new node();
     root->right->right->left = new node();
     for (int i = ; i < ; i++) {
         printancestor(root, i);
         cout << endl;
     }
     return ;
 }