Markdown Table of Contents

Given an array of document lines, generate a table of contents: lines starting with `#` are chapters, lines starting with `##` are sections under the latest chapter, and other lines are ignored. Requirements Input: lines, an array of strings representing document lines. A line starting with # is a chapter. A line starting with ## is a section belonging to the most recent chapter. All other lines are ignored. Output a list of numbered TOC entries: chapter: "1. Title", "2. Title", ... section: "1.1. Title", "1.2. Title", ... under the current chapter Preserve scan order. Notes Check ## before # , or make the chapter check exact enough that a section is not misclassified as a chapter. Reset the section counter whenever a new chapter is encountered. Clarify whether a section can appear before any chapter. A safe implementation can skip it or treat it as invalid, depending on interviewer preference. Preparation Implement with two counters: chapter_count and section_count. Test consecutive chapters, multiple sections under one chapter, ignored body text, and malformed heading strings such as ###.