leetcode 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].
利用bfs解决该问题

/** * 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<double> averageOfLevels(TreeNode* root)     {         queue<TreeNode*> q;                vector<double> res;        q.push(root);        int i =0;        while(!q.empty())        {            double sum = 0;            int s = q.size();            for(int i = 0;i<s;i++)            {                sum+=q.front()->val;                             if(q.front()->left)                  q.push(q.front()->left);              if(q.front()->right)                q.push(q.front()->right);                 q.pop();            }                               double t = sum/s;            res.push_back(t);        }              return res;    }  };