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;
    }  
};