123456789101112131415161718192021222324252627
import { TreeNode } from "../binary-tree-inorder-traversal/TreeNode.ts";import { sum } from "../richest-customer-wealth/sum.ts";
export default function averageOfLevels(root: TreeNode | null): number[] {    if (!root) return [];    const current: TreeNode[] = [root];    const result: number[] = [];
    level(current, (r) => result.push(r));    return result;    // return levelOrder(root).map(v=>sum(v)/v.length)}
function level(nodes: TreeNode[], output: (r: number) => void) {    if (nodes.length === 0) return;
    const values = nodes.map((n) => n.val);    output(sum(values) / values.length);
    level(        nodes            .map((n) => [n.left, n.right].filter(Boolean) as TreeNode[])            .flat(),        output,    );}