flatten bst to ascending linked list.java

import java.util.ArrayList;
import java.util.List;

public class FlattenBstToLinkedList {

    static class Node {
        Node left;
        Node right;
        int val;
    }

    static void flattenTree(List<Node> arr, Node n) {
        if (n == null) {
            return;
        }

        arr.add(n);
        flattenTree(arr, n.left);
        flattenTree(arr, n.right);
    }

    public static void main(String[] args) {
        Node n; // mock tree
        List<Node> arr = new ArrayList<>();
        flattenTree(arr, n);
    }

}