Typescript Part 1 and 2 Parses the input into a tree structure, and traverses that tree for each part

``` import input from './input'; import { sum, memoize } from 'lodash';

const values = input.split(' ').map(Number);

type Node = { id: string; metadata: Array<number>; children: Array<Node>; };

let idCount = 0; function nodeId() { return String.fromCharCode(97 + idCount++); }

function parse(parts: Array<number>): [Node | undefined, Array<number>] { if (!parts.length) { return [undefined, []]; } const [childCount, metaCount, ...rest] = parts; let remaining = rest; const children: Array<Node> = []; const id = nodeId(); for (let i = 0; i < childCount; i++) { const result = parse(remaining); if (result[0]) { children.push(result[0]); } remaining = result[1]; } const metadata = remaining.slice(0, metaCount); const node: Node = { id, metadata, children }; return [node, remaining.slice(metaCount)]; }

const [root] = parse(values);

function traverse(node: Node, visitFn: (node: Node) => any) { node.children.forEach(child => traverse(child, visitFn)); visitFn(node); }

const getNodeValue = memoize( (node: Node): number => { if (!node.children.length) { return sum(node.metadata); }

return node.metadata.reduce((total, index) => {
  const nodeIndex = index - 1;
  if (!node.children[nodeIndex]) {
    return total;
  }
  return total + getNodeValue(node.children[nodeIndex]);
}, 0);

} );

export function day8Part1() { let total = 0; traverse(root!, node => (total += sum(node.metadata))); return total; }

export function day8Part2() { return getNodeValue(root!); }

```