/**

  * Definition for a binary tree node.

  * struct TreeNode {

  *     int val;

  *     TreeNode *left;

  *     TreeNode *right;

  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}

  * };

  */

 class Solution {

 public:

     vector<vector<int>> levelOrder(TreeNode* root) {

         vector<vector<int>> rst;

         vector<int> tmpRst;

         queue<TreeNode*> q;

         if(root) q.push(root);

         int levelcnt=;//当前层元素个数

         int count=;   //下一层元素个数

         while(!q.empty())

         {

             TreeNode* Nd=q.front();

             tmpRst.push_back(Nd->val);

             q.pop();

             --levelcnt;

             if(Nd->left)

             {

                 q.push(Nd->left);

                 ++count;

             }

             if(Nd->right)

             {

                 q.push(Nd->right);

                 ++count;

             }

             if(levelcnt==)

             {

                 levelcnt=count;

                 count=;

                 rst.push_back(tmpRst);

                 tmpRst.clear();

             }

         }

         return rst;

     }

 };