/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    vector<vector<int>> levelOrderBottom(TreeNode* root) {
        vector<vector<int>> result;
        queue<TreeNode* > my_que;
        TreeNode* node = root;
        if(root == nullptr) return result;
        else
        {
            my_que.push(root);
        }
        while(my_que.empty() != 1)
        {
            int size = my_que.size();
            vector<int> nums;
            for(int i=0 ; i<size ;i++ )
            {
                node = my_que.front();
                my_que.pop();
                nums.push_back(node->val);
                if(node->left != nullptr) my_que.push(node->left);
                if(node->right != nullptr) my_que.push(node->right);
            }
            result.push_back(nums);
        }
        //和正常的层次遍历二叉树，多一个反转
        reverse(result.begin(),result.end());
        return result;
    }
};