【LeetCode】107. 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>> levelOrderBottom(TreeNode* root) {        vector<vector<int>> result,r;        vector<int> tmp;        queue<TreeNode*> q;        if(NULL==root)            return r;        if(root!=NULL){             q.push(root);        }        while(!q.empty()){            int size = q.size();            tmp.clear();            while(size--){                TreeNode* node = q.front();                q.pop();                tmp.push_back(node->val);                if(node->left)                    q.push(node->left);                if(node->right)                    q.push(node->right);            }            result.push_back(tmp);        }        reverse(result.begin(),result.end());        return result;    }};