Data Structure Binary Tree: Level order traversal in spiral form

http://www.geeksforgeeks.org/level-order-traversal-in-spiral-form/

 #include <iostream>
 #include <vector>
 #include <algorithm>
 #include <queue>
 #include <stack>
 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 print(node *node) {
     if (!node) return;
     print(node->left);
     cout << node->data << " ";
     print(node->right);
 }

 void printspiral(node* root) {
     if (!root) return;
     bool flag = true;
     stack<node*> S, T;
     S.push(root);
     while (!S.empty()) {
         while (!S.empty()) {
             node *top = S.top();
             S.pop();
             cout << top->data << " ";
             if (!flag) {
                 if (top->left) T.push(top->left);
                 if (top->right) T.push(top->right);
             }
             else {
                 if (top->right) T.push(top->right);
                 if (top->left) T.push(top->left);
             }
         }
         swap(S, T);
         flag = !flag;
     }
 }

 int main() {
     struct 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();
     printspiral(root);
     return ;
 }