leetcode 637 Average of Levels in Binary Tree

python:

class Solution:
    def averageOfLevels(self, root):
        """
        :type root: TreeNode
        :rtype: List[float]
        """
        if root is None:
            return []
        res = []
        queue = [root]
        while(queue):
            sum_level = 0
            l = len(queue)
            for _ in range(l):
                node = queue.pop(0)
                sum_level += node.val
                if node.left:
                    queue.append(node.left)
                if node.right:
                    queue.append(node.right)
            res.append(sum_level/l)
        return res

c++:

class Solution {
public:
    vector<double> averageOfLevels(TreeNode* root) {
        if (root == nullptr)
            return {};
        vector<double> res;
        queue<TreeNode*> q;
        q.push(root);
        
        while(!q.empty()){
            int l = q.size();
            double sum = 0.0;
            for (int i=0; i<l; i++){
                TreeNode* f = q.front();
                q.pop();
                sum += f->val;
                if(f->left) 
                    q.push(f->left);
                if(f->right)
                    q.push(f->right);
            }
            res.push_back(sum/l);
        }
        return res;
     }
};