力扣——N叉树的后序遍历

/*
// Definition for a Node.
class Node {
    public int val;
    public List<Node> children;

    public Node() {}

    public Node(int _val,List<Node> _children) {
        val = _val;
        children = _children;
    }
};
*/
class Solution {
    List<Integer> list = new ArrayList<>();
    public List<Integer> postorder(Node root) {
        if(root==null){return list;}
        scanPre(root);
        list.add(root.val);
        return list;
    }

    public void scanPre(Node node){
        if(node.children.size()==0){return;}
        if(node.children.size()>0){
            for(Node n:node.children){
                scanPre(n);
                list.add(n.val);
            }
        }
    }
}