二叉树层序遍历

基本思路: 头节点先入队,poll()则打印,如果有左有孩子,入队 ....  

    //层序遍历
    public static void levelVisit(Node node){
        Queue<Node> qe = new LinkedList<>();
        qe.add(node);
        while (!qe.isEmpty()){
            Node cur = qe.poll();
            System.out.print(cur.val + " ");
            if (cur.left != null){
                qe.add(cur.left);
            }
            if(cur.right != null){
                qe.add(cur.right);
            }
        }
    }