[LeetCode] Maximum depth of Binary Tree

Given a binary tree, find its maximum depth.
The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

Java code:

 public int maxDepth(TreeNode root) {
        if(root == null) return 0;
        
        int max = 0;
        Queue tmp = new LinkedList();
        tmp.add(root);
        
        while(!tmp.isEmpty()){
            max++;
            int size = tmp.size();
            for(int i = 0; i < size; i++){
                TreeNode node = tmp.poll();
                if(node.left != null) tmp.add(node.left);
                if(node.right != null) tmp.add(node.right);
            }
        }
        
        return max;
    }