Build a BFS Web Crawler with Robust Retry and URL Normalization

You are given an initial URL start_url. Build an HTTP crawler that performs a breadth‑first traversal of the pages reachable from that URL. The program must read three lines from standard input and output the result as described below. Requirements Traversal order – Visit pages in BFS order starting from start_url. Maintain a set of already‑seen URLs so you never fetch the same page twice. Normalisation – Before comparing or enqueuing a URL, convert relative links to…