#include <iostream>

#include <algorithm>

#include <vector>

#include <stack>

using namespace std;

struct TreeNode {

    int val;

    TreeNode *left;

    TreeNode *right;

    TreeNode(int x): val(x), left(NULL), right(NULL){}

}; 

class Solution {

public:

    vector<int> postorderTraversal(TreeNode *root) {

        vector<int> res;

        stack<TreeNode *> s;

        if (!root) {

            return res;

        }

        s.push(root);

        while (!s.empty()) {

            TreeNode *p = s.top(); s.pop();

            res.push_back(p->val);

            if (p->right) {

                s.push(p->right);

            }

            if (p->left) {

                s.push(p->left);

            }

        }

        reverse(res.begin(), res.end());

        return res;

    }

};

int main(int argc, char *argv[]) {

    TreeNode *p = new TreeNode();

    p->right = new TreeNode();

    p->left = new TreeNode();    

    Solution *solution = new Solution();

    vector<int> res;

    res = solution->postorderTraversal(p);

    vector<int>::iterator it;

    for (it = res.begin(); it != res.end(); it++) {

        cout << *it << endl;

    }

}