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].

Solution: Using Level Order Traversal

Note: Use double as the type of sum in case there's overflow

    vector<double> averageOfLevels(TreeNode* root) {
        vector<double> ans;
        queue<TreeNode *> q;
        q.push(root);

        while (!q.empty()) {
            int size = q.size();
            double sum = 0;

            for (int i=0; i<size; i++) {
                TreeNode *node = q.front();
                q.pop();

                if (node->left) q.push(node->left);
                if (node->right) q.push(node->right);
                sum += node->val;
            }

            ans.push_back(sum/size);
        }
        return ans;
    }