[해커랭크] Tree: Postorder Traversal [JAVA]

문제링크 : www.hackerrank.com/challenges/tree-postorder-traversal/problem

Tree: Postorder Traversal | HackerRank

    public static void postOrder(Node root) {
        if(root==null) return;
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.data + " ");
    }