标签：
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;
traversal(root,1,result);
reverse(result.begin(),result.end()); //在原先的题的基础上reverse一下即可
return result;
}
//先序遍历 压入结果
void traversal(TreeNode *node,int level,vector<vector<int>> &result)
{
if(node==NULL) return;
if(level>result.size())
result.push_back(vector<int>());
result[level-1].push_back(node->val);
traversal(node->left,level+1,result);
traversal(node->right,level+1,result);
}
};
LeetCode:Binary Tree Level Order Traversal II (按层遍历)
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原文地址：http://www.cnblogs.com/xiaoying1245970347/p/4724707.html
