LeetCode Binary Tree Level Order Traversal II

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

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

    3
   / 
  9  20
    /  
   15   7

return its bottom-up level order traversal as:

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

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public List<List<Integer>> levelOrderBottom(TreeNode root) {
            LinkedList<List<Integer>> resList= new LinkedList<>();
            
            if (root==null) {
                return resList;
            }
            
            Deque<TreeNode> visitDeque=new LinkedList<>();
            List<Integer>    currList;
            visitDeque.add(root);
            int count=1;
            int level=0;
            while (!visitDeque.isEmpty()) {
                level=0;
                currList=new ArrayList<Integer>();
                for (int i = 0; i < count; i++) {
                    TreeNode     node=visitDeque.pop();
                    currList.add(node.val);
                    if (node.left != null) {
                        ++level;
                        visitDeque.add(node.left);
                    }
                    if (node.right != null) {
                        ++level;
                        visitDeque.add(node.right);
                    }
                }
                count=level;
                resList.addFirst(currList);
            }
            return resList;
    }
}