C++ super easy 11-line solution, beats 100%!
vector<int> postorder(Node* root) {\n        if(root==NULL) return {};\n        vector<int> res;\n        stack<Node*> stk;\n        stk.push(root);\n        wh
    vector<int> postorder(Node* root) {\n        if(root==NULL) return {};\n        vector<int> res;\n        stack<Node*> stk;\n        stk.push(root);\n        while(!stk.empty())\n        {\n            Node* temp=stk.top();\n            stk.pop();\n            for(int i=0;i<temp->children.size();i++) stk.push(temp->children[i]);\n            res.push_back(temp->val);\n        }\n        reverse(res.begin(), res.end());\n        return res;\n    }
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