simple solution ||  beats 100%
Intuition\n Describe your first thoughts on how to solve this problem. \n\n# Approach\n Describe your approach to solving the problem. \n\n# Complexity\n- Time 
# Intuition\n<!-- Describe your first thoughts on how to solve this problem. -->\n\n# Approach\n<!-- Describe your approach to solving the problem. -->\n\n# Complexity\n- Time complexity:\n<!-- Add your time complexity here, e.g. $$O(n)$$ -->\n\n- Space complexity:\n<!-- Add your space complexity here, e.g. $$O(n)$$ -->\n\n# Code\n```java []\n/*\n// Definition for a Node.\nclass Node {\n    public int val;\n    public List<Node> children;\n\n    public Node() {}\n\n    public Node(int _val) {\n        val = _val;\n    }\n\n    public Node(int _val, List<Node> _children) {\n        val = _val;\n        children = _children;\n    }\n};\n*/\n\nclass Solution {\n    public List<Integer> postorder(Node root) {\n        List<Integer> list=new ArrayList<>();\n        if(root==null) return list;\n        return  post_order(root,list);\n    }\n    public List<Integer> post_order(Node node,List<Integer> list){\n      for(Node child:node.children){\n        if(child!=null){\n            post_order(child,list);\n        }\n      }\n      list.add(node.val);\n      return list;\n    }\n}\n```
['Java']