#### Overview of this book

Java 9 Data Structures and Algorithms covers classical, functional, and reactive data structures, giving you the ability to understand computational complexity, solve problems, and write efficient code. This book is based on the Zero Bug Bounce milestone of Java 9. We start off with the basics of algorithms and data structures, helping you understand the fundamentals and measure complexity. From here, we introduce you to concepts such as arrays, linked lists, as well as abstract data types such as stacks and queues. Next, we’ll take you through the basics of functional programming while making sure you get used to thinking recursively. We provide plenty of examples along the way to help you understand each concept. You will also get a clear picture of reactive programming, binary searches, sorting, search trees, undirected graphs, and a whole lot more!
Java 9 Data Structures and Algorithms
Credits
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Preface
Free Chapter
Why Bother? – Basic
Cogs and Pulleys – Building Blocks
Protocols – Abstract Data Types
Detour – Functional Programming
Efficient Searching – Binary Search and Sorting
Efficient Sorting – quicksort and mergesort
Concepts of Tree
More About Search – Search Trees and Hash Tables
Concepts of Graph
Reactive Programming
Index

## Sorting

Okay, so we are convinced that if we have a sorted array, it takes a lot less time to find an element in it. But how do we get a sorted array? An arbitrary array is unlikely to be sorted. The algorithm of getting a sorted array out of an arbitrary array while keeping all the elements same, that is, by only rearranging the elements of an input array, is called sorting. There are a lot of algorithms for sorting. But in this chapter, we will start with a few simple ones that are not efficient. In the next chapter, we will explore efficient sorting algorithms.

### Selection sort

This is the most natural algorithm for sorting. We choose each position of the array and find the element in the array that belongs in that position. The functional definition of selection sort is as follows:

• Find the minimum element in an array

• Swap this element with the first element of the array

• Sort the rest of the array after the first element recursively

Finding the minimum element has the functional structure as...