1class TreeNode {
2    constructor(val, left = null, right = null) {
3        this.val = val;
4        this.left = left;
5        this.right = right;
6    }
7}
8
9function averageOfLevels(root) {
10    const averages = [];
11    const queue = [root];
12    while (queue.length > 0) {
13        const count = queue.length;
14        let sum = 0;
15        for (let i = 0; i < count; i++) {
16            const node = queue.shift();
17            sum += node.val;
18            if (node.left) queue.push(node.left);
19            if (node.right) queue.push(node.right);
20        }
21        averages.push(sum / count);
22    }
23    return averages;
24}
25
26// Example usage
27const a = new TreeNode(3);
28const b = new TreeNode(9);
29const c = new TreeNode(20);
30const d = new TreeNode(15);
31const e = new TreeNode(7);
32
33a.left = b;
34a.right = c;
35c.left = d;
36c.right = e;
37
38console.log(averageOfLevels(a));

using System.Collections.Generic;

public class TreeNode {
    public int val;
    public TreeNode left;
    public TreeNode right;
    public TreeNode(int x) { val = x; }
}

public class Solution {
    public IList<double> AverageOfLevels(TreeNode root) {
        List<long> sums = new List<long>();
        List<int> counts = new List<int>();
        dfs(root, 0, sums, counts);
        List<double> averages = new List<double>();
        for (int i = 0; i < sums.Count; i++) {
            averages.Add((double)sums[i] / counts[i]);
        }
        return averages;
    }
    
    private void dfs(TreeNode node, int level, List<long> sums, List<int> counts) {
        if (node == null) return;
        if (level == sums.Count) {
            sums.Add(node.val);
            counts.Add(1);
        } else {
            sums[level] += node.val;
            counts[level]++;
        }
        dfs(node.left, level + 1, sums, counts);
        dfs(node.right, level + 1, sums, counts);
    }
    
    public static void Main(string[] args) {
        TreeNode a = new TreeNode(3);
        TreeNode b = new TreeNode(9);
        TreeNode c = new TreeNode(20);
        TreeNode d = new TreeNode(15);
        TreeNode e = new TreeNode(7);
        a.left = b;
        a.right = c;
        c.left = d;
        c.right = e;
        
        Solution solution = new Solution();
        IList<double> result = solution.AverageOfLevels(a);
        foreach (double avg in result) {
            Console.Write(avg + " ");
        }
    }
}