Data Structure Binary Tree: Iterative Postorder Traversal

http://www.geeksforgeeks.org/iterative-postorder-traversal-using-stack/
 1 #include <iostream>
 2 #include <vector>
 3 #include <algorithm>
 4 #include <queue>
 5 #include <stack>
 6 #include <string>
 7 #include <fstream>
 8 #include <map>
 9 using namespace std;
10 
11 struct node {
12     int data;
13     struct node *left, *right;
14     node() : data(0), left(NULL), right(NULL) { }
15     node(int d) : data(d), left(NULL), right(NULL) { }
16 };
17 
18 void prints(node *root) {
19     if (!root) return;
20     stack<node*> S;
21     do {
22         while (root) {
23             if (root->right) S.push(root->right);
24             S.push(root);
25             root = root->left;
26         }
27         root = S.top();
28         S.pop();
29         if (root->right && !S.empty() && root->right == S.top()) {
30             S.pop();
31             S.push(root);
32             root = root->right;
33         }
34         else {
35             cout << root->data << " ";
36             root = NULL;
37         }
38     } while (!S.empty());
39 }
40 
41 int main() {
42     node *root = new node(1);
43     root->left = new node(2);
44     root->right = new node(3);
45     root->left->left = new node(4);
46     root->left->right = new node(5);
47     root->right->left = new node(6);
48     root->right->right = new node(7);
49     prints(root);
50     return 0;
51 }