* struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 * };
 */

class Solution {
public:
    /**
     * 
     * @param root TreeNode类 
     * @return int整型vector
     */
    void postorder(vector<int>& v, TreeNode* Node)
    {
        if (Node == nullptr)
            return ;
        postorder(v, Node->left);
        postorder(v, Node->right);
        v.push_back(Node->val);
    }
    vector<int> postorderTraversal(TreeNode* root) {
        // write code here
        vector<int> v;
        postorder(v,root);
        return v;
    }
};