Java for Leetcode 107 Binary Tree level Order traversal II

Given a binary tree, return the bottom-up level order traversal of its nodes ' values. (ie, from the left-to-right, the level by level from the leaf to root).

For example:
Given binary Tree {3,9,20,#,#,15,7} ,

    3   /   9    /   7

Return its bottom-up level order traversal as:

[  [15,7],  [9,20],  [3]]

Problem Solving Ideas:

Modify the Java for Leetcode 102 Binary Tree level Order traversal can be resolved, Java implementation is as follows:

    Public list<list<integer>> Levelorderbottom (TreeNode root) {    list<list<integer>> List = New Arraylist<list<integer>> ();    if (root = null)        return list;    queue<treenode> queue = new linkedlist<treenode> ();    Queue.add (root);    while (Queue.size ()! = 0) {        list<integer> alist = new arraylist<integer> ();        for (TreeNode child:queue)            alist.add (child.val);        List.add (New arraylist<integer> (alist));        Queue<treenode> Queue2=queue;        Queue=new linkedlist<treenode> ();        for (TreeNode child:queue2) {            if (child.left! = null)                queue.add (child.left);            if (child.right! = null)                queue.add (child.right);}    }    Collections.reverse (list);    return list;    }

Java for Leetcode 107 Binary Tree level Order traversal II