Book Image

Java 9 Data Structures and Algorithms

By : Debasish Ray Chawdhuri
Book Image

Java 9 Data Structures and Algorithms

By: Debasish Ray Chawdhuri

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!
Table of Contents (19 chapters)
Java 9 Data Structures and Algorithms
Credits
About the Author
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface
Index

Sorting using a priority queue


Since a priority queue always returns the minimum element, if we insert all input elements and then keep dequeuing them, they would be dequeued in sorted order. This can be used to sort a list of elements. In our example, we will add a new method called the LinkedList implementation. This implementation sorts the elements using PriorityQueue. First insert all the elements into the priority queue. Then, dequeue the elements and append them back to the linked list:

public void sort(Comparator<E> comparator){
    PriorityQueue<E> priorityQueue = new LinkedHeap<E>(comparator);

    while (first!=null){
        priorityQueue.enqueue(getFirst());
        removeFirst();
    }

    while (priorityQueue.checkMinimum()!=null){
        appendLast(priorityQueue.dequeueMinimum());
    }
}

Both enqueue and dequeue have θ(lg n) complexity, and we have to enqueue and dequeue each of the elements. We have already seen this: lg 1 + lg 2 + … + lg n = θ(n lg n...