590. N-ary Tree Postorder Traversal

QUESTION:

Given an n-ary tree, return the postorder traversal of its nodes’ values.

For example, given a 3-ary tree:

img

Return its postorder traversal as: [5,6,3,2,4,1].

Note:

Recursive solution is trivial, could you do it iteratively?

EXPLANATION:

就和之前的先序排列一样，这个是后序排列，只需要在最后的时候添加到list的操作就可以。

SOLUTION:

    static List<Integer> postorderResult = new ArrayList<>();

    public static List<Integer> postorder(Node root) {
        if(root == null) return null;
        for(int i = 0;i<root.children.size();i++){
            postorder(root.children.get(i));
        }
        postorderResult.add(root.val);
        return postorderResult;
    }
--> return <--