Leetcode--Binary Tree Level Order Traversal II

Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by level from leaf to root).
For example:

Given binary tree

{3,9,20,#,#,15,7}

,

3
/ \
9  20
/  \
15   7

return its bottom-up level order traversal as:

[
[15,7],
[9,20],
[3]
]

confused what

"{1,#,2,3}"

means? >
read more on how binary tree is serialized on OJ.

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/**
* 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> > levelOrderBottom(TreeNode *root) {
vector<vector<int>> res;
if(root==NULL)
return res;

deque<TreeNode*> que;
que.push_back(root);
while(!que.empty())
{
vector<int> temp;
deque<TreeNode*> cur;
while(!que.empty())
{
temp.push_back(que.front()->val);
if(que.front()->left!=NULL)
cur.push_back(que.front()->left);
if(que.front()->right!=NULL)
cur.push_back(que.front()->right);
que.pop_front();
}
res.insert(res.begin(),temp);//问题一中的后插，改成头插法
que.assign(cur.begin(),cur.end());
}

return res;
}
};