33 N-ary Tree Postorder Traversal

The height of the n-ary tree is less than or equal to 1000
The total number of nodes is between [0, 10^4]

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

    public Node() {}

    public Node(int _val) {
        val = _val;
    }

    public Node(int _val, List<Node> _children) {
        val = _val;
        children = _children;
    }
};
*/

class Solution {
	// 存放结果
    List<Integer> list = new ArrayList<>();
    public List<Integer> postorder(Node root) {
    	// 递归终点
        if (root == null)
            return list;
        // 递归遍历其他节点
        for(Node node: root.children)
            postorder(node);
        // 遍历根节点
        list.add(root.val);
        return list;
    }
}