LeetCode:Binary Tree Level Order Traversal II (按层遍历)-白红宇

LeetCode:Binary Tree Level Order Traversal II (按层遍历)

阅读量：6709 次

发布时间：2019-06-25

本文共 1212 字，大约阅读时间需要 4 分钟。

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
     
      
       > levelOrderBottom(TreeNode* root) {        vector
       
        
         > 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
         
          
           > &result) { if(node==NULL) return; if(level>result.size()) result.push_back(vector
           
            ()); result[level-1].push_back(node->val); traversal(node->left,level+1,result); traversal(node->right,level+1,result); }};