102 Binary Tree Level Order Traversal

/**
* 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>> res;
if(root==NULL)
return res;
vector<int> r;
queue<TreeNode*> tmp;
tmp.push(root);
queue<TreeNode*> tmp1;
while(!tmp.empty())
{
r.clear();
while(!tmp.empty())
{
TreeNode* hehe = tmp.front();
r.push_back(hehe->val);
if(hehe->left!=NULL)
tmp1.push(hehe->left);
if(hehe->right!=NULL)
tmp1.push(hehe->right);
tmp.pop();
}
tmp = tmp1;
while(!tmp1.empty())
tmp1.pop();
res.push_back(r);
}
return res;
}
};