Web Crawler is a bot that downloads the content from the internet and indexes it. The main purpose of this bot is to learn about the different web pages on the internet. This kind of bots is mostly operated by search engines. By applying the search algorithms to the data collected by the web crawlers, search engines can provide the relevant links as the response for the request requested by the user. In this article, let’s discuss how the web crawler is implemented.
Webcrawler is a very important application of the Breadth-First Search Algorithm. The idea is that the whole internet can be represented by a directed graph:
- with vertices -> Domains/ URLs/ Websites.
- edges -> Connections.
Approach: The idea behind the working of this algorithm is to parse the raw HTML of the website and look for other URL in the obtained data. If there is a URL, then add it to the queue and visit them in breadth-first search manner.
Note: This code will not work on an online IDE due to proxy issues. Try to run on your local computer.
Website found: https://www.google.com Website found: https://www.facebook.com Website found: https://www.amazon.com Website found: https://www.microsoft.com Website found: https://www.apple.com
Applications: This kind of web crawler is used to acquire the important parameters of the web like:
- What are the frequently visited websites?
- What are the websites that are important in the network as a whole?
- Useful Information on social networks: Facebook, Twitter… etc.
- Who is the most popular person in a group of people?
- Who is the most important software engineer in a company?
- Find intersection of intervals given by two lists
- Check if given Parentheses expression is balanced or not
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