/**

 * Definition of TreeNode:

 * class TreeNode {

 * public:

 *     int val;

 *     TreeNode *left, *right;

 *     TreeNode(int val) {

 *         this->val = val;

 *         this->left = this->right = NULL;

 *     }

 * }

 */

class Solution {

    /**

     * @param root: The root of binary tree.

     * @return: Level order a list of lists of integer

     */

    /*

    二叉树最基本的层次遍历方式；

    */

public:

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

        // write your code here

        vector<vector<int>> vec;

        if(root==NULL){

            return vec;

        }

        queue<TreeNode*> que;

        que.push(root);

        while(!que.empty()){

            int count=que.size();

            vector<int> vec_temp;

            while(count--){

                TreeNode* temp=que.front();

                que.pop();

                vec_temp.push_back(temp->val);

                if(temp->left){

                    que.push(temp->left);

                }

                if(temp->right){

                    que.push(temp->right);

                }

            }

            vec.push_back(vec_temp);

        }

        return vec;

    }

};