Web Crawler Same Host

You are given a starting URL start_url and the pages of an in-memory web: pages[i] is a URL and links[i] lists the URLs found on that page. A URL that is not in pages has no links.

Implement a web crawler that returns all URLs reachable from start_url that share the same hostname as start_url. The order of URLs in the result does not matter.

Your function:

def crawl(start_url: str, pages: list[str], links: list[list[str]]) -> list[str]:
    pass

Requirements:

• Start from start_url.
• Avoid duplicates: never crawl the same URL twice.
• Restrict scope: only follow URLs whose hostname matches that of start_url.
• Assume all URLs use the http protocol and do not include a port.
• Do not require URL normalization beyond exact string matching.
• Treat URL fragments as part of the URL string; if they appear, they are distinct URLs unless they are exact duplicates.

Example 1:
Input:

• start_url = "http://news.example.com/"
• pages = ["http://news.example.com/", "http://news.example.com/a", "http://news.example.com/b"]
• links = [["http://news.example.com/a", "http://news.example.com/b", "http://other.com/x"], ["http://news.example.com/b"], []]

Output: ["http://news.example.com/", "http://news.example.com/a", "http://news.example.com/b"]

Example 2:
Input:

• start_url = "http://example.com/index"
• pages = ["http://example.com/index", "http://example.com/index#top", "http://example.com/about"]
• links = [["http://example.com/index#top", "http://example.com/about"], [], []]

Output: ["http://example.com/index", "http://example.com/index#top", "http://example.com/about"]