按之字形打印二叉树

看到和自己一样的思路，就先记下来，
我用的vector记录每一层的结点，结果内存爆了
用队列方便
原文链接
https://www.nowcoder.com/profile/6614408/codeBookDetail?submissionId=16362055

vector<vector<int> > Print(TreeNode* pRoot) {
        vector<vector<int>>res;

        if(pRoot == NULL) return res;

        queue<TreeNode *>que;
        que.push(pRoot);
        bool flog = false;

        while(!que.empty())
        {
            vector<int>vec;
            const int size = que.size();

            for(int i=0;i<size;i++)
            {
                TreeNode * tmp = que.front();
                que.pop();
                vec.push_back(tmp->val);

                if(tmp->left)
                    que.push(tmp->left);
                if(tmp->right)
                    que.push(tmp->right);
            }
            if(flog)
                std::reverse(vec.begin(),vec.end());
            res.push_back(vec);

            flog = !flog;
        }
        return res;
    }