/**
 * 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>> printFromTopToBottom(TreeNode* root) {
        vector<vector<int>>res;
        if(!root)
            return res;
        queue<TreeNode*>que_;
        que_.push(root);
        while(!que_.empty())
        {
            int num=que_.size();
            vector<int>tmp;
            while(num--)
            {
                TreeNode *visit=que_.front();
                tmp.push_back(visit->val);
                if(visit->left)
                    que_.push(visit->left);
                if(visit->right)
                    que_.push(visit->right);
                que_.pop();
            }
            res.push_back(tmp);
        }
        return res;
    }
};