leetcode——117. 填充每个节点的下一个右侧节点指针 II

public Node connect(Node root) {
        if(root == null){
            return root;
        }
        Queue<Node> Q = new LinkedList<>();
        Q.add(root);
        while (Q.size() > 0){
            int size = Q.size();
            for(int i = 0;i<size;i++){
                Node node = Q.poll();
                if(i<size -1){
                    node.next = Q.peek();
                }
                if(node.left != null){
                    Q.add(node.left);
                }
                if(node.right != null){
                    Q.add(node.right);
                }
            }
        }
        return root;
    }