Binary Tree Level Order Traversal

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

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

    3
   / \
  9  20
    /  \
   15   7

return its level order traversal as:

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

confused what "{1,#,2,3}" means? > read more on how binary tree is serialized on OJ.

許久未練,　生疏不少.　歎~

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector > levelOrder(TreeNode *root)
    {
        vector vee;
        vector>ve;
        queue qu;
        TreeNode *no;
        if(NULL==root)
            return ve;
        qu.push(root);
        int len = qu.size();
        while(len!=0)
        {
            while(len--)
            {
                no = qu.front();
                qu.pop();
                vee.push_back(no->val);
                if(NULL!=no->left)qu.push(no->left);
                if(NULL!=no->right)qu.push(no->right);
            }
            ve.push_back(vee);
            vee.clear();
            len = qu.size();
        }
        return ve;
    }
};