【LeetCode】Binary Tree Level Order Traversal-优快云博客

本文深入解析了C++实现的二叉树层次遍历算法，包括题目描述、代码示例及关键知识点总结，帮助读者理解并掌握二叉树层次遍历的基本原理与实践。

题目描述

Binary Tree Level Order Traversal

Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level).

For example:
Given binary tree {3,9,20,#,#,15,7},

return its level order traversal as:

[
  [3],
  [9,20],
  [15,7]
]

confused what "{1,#,2,3}" means? > read more on how binary tree is serialized on OJ.

题目分析

树按层遍历

总结

使用队列

代码示例

#include 
   
    
#include 
    
     
#include 
     
      
using namespace std;

struct TreeNode {
     int val;
     TreeNode *left;
     TreeNode *right;
     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 };
class Solution {
public:
    vector
      
       
         > levelOrder(TreeNode *root) {
        vector
        
         
           > ret; if(root == NULL) return ret; queue
          
            quTree; quTree.push(root); int levelsum = 1;//同一层有多少个结点 vector
           
             tmp; while(!quTree.empty()) { TreeNode* cur = quTree.front(); tmp.push_back(cur->val); quTree.pop(); levelsum--; if(cur->left != NULL) quTree.push(cur->left); if(cur->right != NULL) quTree.push(cur->right); if(levelsum == 0)//本层结束，开始下一层 { levelsum = quTree.size(); ret.push_back(tmp); tmp.clear(); } } return ret; } }; void printvec(vector
            
              A) { for(int i = 0;i
             
               > A, char *name) { printf("%s\n",name); for(int i = 0;i
              
                > out = so.levelOrder(&node1); printvecvec(out,"ret"); } int main(int argc, char *argv[]) { test0(); return 0; }