/**

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

vector<vector<int>> result;

if(!root) return result;

queue<pair<TreeNode*, int>> level_queue;

vector<int> tmp_vec;

level_queue.push(make_pair(root,1));

int level = 1;

while(!level_queue.empty()){

pair<TreeNode*,int> p = level_queue.front();

level_queue.pop();

if(p.second != level){

result.push_back(tmp_vec);

level = p.second;

tmp_vec.clear();

}

tmp_vec.push_back(p.first->val);

if(p.first->left != NULL) level_queue.push(make_pair(p.first->left, p.second+1));

if(p.first->right != NULL) level_queue.push(make_pair(p.first->right, p.second+1));

}

result.push_back(tmp_vec);

return result;

}

};