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  • 637. Average of Levels in Binary Tree

    Given a non-empty binary tree, return the average value of the nodes on each level in the form of an array.

    Example 1:

    Input:
        3
       / 
      9  20
        /  
       15   7
    Output: [3, 14.5, 11]
    Explanation:
    The average value of nodes on level 0 is 3,  on level 1 is 14.5, and on level 2 is 11. Hence return [3, 14.5, 11].

    (1)思想1:使用queue ,对二叉树进行层遍历。

    C++:

     1 /**
     2  * Definition for a binary tree node.
     3  * struct TreeNode {
     4  *     int val;
     5  *     TreeNode *left;
     6  *     TreeNode *right;
     7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
     8  * };
     9  */
    10 class Solution {
    11 public:
    12     vector<double> averageOfLevels(TreeNode* root) {
    13         vector<double> res;
    14         queue<TreeNode*> q{{root}};
    15         while(!q.empty())
    16         {
    17             int n=q.size();
    18             double sum=0;
    19             for(int i=0;i<n;i++)
    20             {
    21                 TreeNode *t=q.front();
    22                 q.pop();
    23                 sum=sum+t->val;
    24                 if(t->left)
    25                     q.push(t->left);
    26                 if(t->right)
    27                     q.push(t->right);
    28             }
    29             res.push_back(sum/n);
    30         }
    31         return res;
    32      
    33     }
    34 };
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  • 原文地址:https://www.cnblogs.com/sword-/p/8059925.html
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