Data Structure Binary Tree: Iterative Postorder Traversal

http://www.geeksforgeeks.org/iterative-postorder-traversal-using-stack/

#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(0), left(NULL), right(NULL) { }
    node(int d) : data(d), left(NULL), right(NULL) { }
};

void prints(node *root) {
    if (!root) return;
    stack<node*> S;
    do {
        while (root) {
            if (root->right) S.push(root->right);
            S.push(root);
            root = root->left;
        }
        root = S.top();
        S.pop();
        if (root->right && !S.empty() && root->right == S.top()) {
            S.pop();
            S.push(root);
            root = root->right;
        }
        else {
            cout << root->data << " ";
            root = NULL;
        }
    } while (!S.empty());
}

int main() {
    node *root = new node(1);
    root->left = new node(2);
    root->right = new node(3);
    root->left->left = new node(4);
    root->left->right = new node(5);
    root->right->left = new node(6);
    root->right->right = new node(7);
    prints(root);
    return 0;
}