剑指offer：把二叉树打印成多行

题目：
从上到下按层打印二叉树，同一层结点从左至右输出。每一层输出一行。
代码：

class Solution {
public:
    vector<vector<int> > Print(TreeNode* pRoot) 
    {
        vector<vector<int> > res;
        if(NULL == pRoot)
        {
            return res;
        }
        queue<TreeNode *> que;
        que.push(pRoot);
        while(!que.empty())
        {
            vector<TreeNode *> vecTmp;
            vector<int> tmp;
            while(!que.empty())
            {
                TreeNode * tmp = que.front();
                que.pop();
                vecTmp.push_back(tmp);
            }
            for(int i=0; i<vecTmp.size(); ++i)
            {
                tmp.push_back(vecTmp[i]->val);
                if(NULL != vecTmp[i]->left)
                {
                    que.push(vecTmp[i]->left);
                }
                if(NULL != vecTmp[i]->right)
                {
                    que.push(vecTmp[i]->right);
                }
            }
            res.push_back(tmp);
        }
        return res;
    }
};