Given a binary tree, return the postorder traversal of its nodes' values.

class Solution {

public:

    vector<int> postorderTraversal(TreeNode *root)

    {      

        vector<int> result;

        stack<TreeNode*> tempStack;

        TreeNode *dummyRootNode  = root;

        if(dummyRootNode == NULL)

            return result;

        tempStack.push(dummyRootNode);

        while(!tempStack.empty())

        {

            TreeNode *tempNode = tempStack.top();

            tempStack.pop();

            result.push_back(tempNode->val);

            if(tempNode1->left) tempStack.push(tempNode->left);

            if(tempNode1->right) tempStack.push(tempNode->right);

        }

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

        return result;

    }

};