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class Solution {  
public:  
    vector<int> postorderTraversal(TreeNode *root) {  
        // IMPORTANT: Please reset any member data you declared, as  
        // the same Solution instance will be reused for each test case.  
        vector<int> result;  
        result.clear();  
        if (NULL != root) {  
            Traversal(root->left, result);  
            Traversal(root->right, result);  
            result.push_back(root->val);  
        }  
        return result;  
    }  
    
    void Traversal(TreeNode * now, vector<int>& result) {  
        if (NULL != now) {  
            Traversal(now->left, result);  
            Traversal(now->right, result);  
            result.push_back(now->val);  
        }  
    }  
};