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]
]

/** * 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>> finsh;    void levelsort(TreeNode* root, int level){        if(!root)          return ;        if(level == finsh.size())         {            vector<int> add;            finsh.push_back(add);         }        finsh[level].push_back(root->val);        levelsort(root->left, level+1);        levelsort(root->right, level+1);    }    vector<vector<int>> levelOrderBottom(TreeNode* root) {        levelsort(root, 0);        return vector<vector<int> >(finsh.rbegin(), finsh.rend());    }};

反向迭代器参考：