/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
 public:
  vector<double> averageOfLevels(TreeNode* root) {
    vector<double> ans;
    queue<TreeNode*> q{{root}};

    while (!q.empty()) {
      long sum = 0;
      const int size = q.size();
      for (int i = 0; i < size; ++i) {
        TreeNode* node = q.front();
        q.pop();
        sum += node->val;
        if (node->left)
          q.push(node->left);
        if (node->right)
          q.push(node->right);
      }
      ans.push_back(sum / (double)size);
    }

    return ans;
  }
};