July 2017
Beginner to intermediate
155 pages
3h 21m
English
Content preview from Think Data StructuresBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Chapter 7. Getting to Philosophy
The goal of this chapter is to develop a web crawler that tests the “Getting to Philosophy” conjecture, which I presented in “Search Engines”.
Getting Started
In the repository for this book, you’ll find some code to help you get started:
WikiNodeExample.javacontains the code from the previous chapter, demonstrating recursive and iterative implementations of depth-first search (DFS) in a DOM tree.WikiNodeIterable.javacontains anIterableclass for traversing a DOM tree. I’ll explain this code in the next section.WikiFetcher.javacontains a utility class that uses jsoup to download pages from Wikipedia. To help you comply with Wikipedia’s terms of service, this class limits how fast you can download pages; if you request more than one page per second, it sleeps before downloading the next page.WikiPhilosophy.javacontains an outline of the code you will write for this exercise.
You’ll also find the Ant build file build.xml. If you run ant WikiPhilosophy, it will run a simple bit of starter code.
Iterables and Iterators
In the previous chapter, I presented an iterative depth-first search (DFS), and suggested that an advantage of the iterative version, compared to the recursive version, is that it is easier to wrap in an Iterator object. In this section we’ll see how to do that.
If you are not familiar with the Iterator and Iterable interfaces, you can read about them at http://thinkdast.com/iterator and http://thinkdast.com/iterable.
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.