40 Algorithms Every Programmer Should Know

▶Book Description
Algorithms have always played an important role in both the science and practice of computing. Beyond traditional computing, the ability to use algorithms to solve real-world problems is an important skill that any developer or programmer must have. This book will help you not only to develop the skills to select and use an algorithm to solve real-world problems but also to understand how it works.

You'll start with an introduction to algorithms and discover various algorithm design techniques, before exploring how to implement different types of algorithms, such as searching and sorting, with the help of practical examples. As you advance to a more complex set of algorithms, you'll learn about linear programming, page ranking, and graphs, and even work with machine learning algorithms, understanding the math and logic behind them. Further on, case studies such as weather prediction, tweet clustering, and movie recommendation engines will show you how to apply these algorithms optimally. Finally, you'll become well versed in techniques that enable parallel processing, giving you the ability to use these algorithms for compute-intensive tasks.

By the end of this book, you'll have become adept at solving real-world computational problems by using a wide range of algorithms.

▶What You Will Learn
- Explore existing data structures and algorithms found in Python libraries
- Implement graph algorithms for fraud detection using network analysis
- Work with machine learning algorithms to cluster similar tweets and process Twitter data in real time
- Predict the weather using supervised learning algorithms
- Use neural networks for object detection
- Create a recommendation engine that suggests relevant movies to subscribers
- Implement foolproof security using symmetric and asymmetric encryption on Google Cloud Platform (GCP)

▶Key Features
- Learn the techniques you need to know to design algorithms for solving complex problems
- Become familiar with neural networks and deep learning techniques
- Explore different types of algorithms and choose the right data structures for their optimal implementation

▶Who This Book Is For
This book is for the serious programmer! Whether you are an experienced programmer looking to gain a deeper understanding of the math behind the algorithms or have limited programming or data science knowledge and want to learn more about how you can take advantage of these battle-tested algorithms to improve the way you design and write code, you'll find this book useful. Experience with Python programming is a must, although knowledge of data science is helpful but not necessary.

▶What this book covers
- Chapter 1, Overview of Algorithms, summarizes the fundamentals of algorithms. It starts with a section on the basic concepts needed to understand the working of different algorithms. It summarizes how people started using algorithms to mathematically formulate certain classes of problems. It also mentions the limitations of different algorithms. The next section explains the various ways to specify the logic of an algorithm. As Python is used in this book to write the algorithms, how to set up the environment in order to run the examples is explained next. Then, the various ways in which an algorithm's performance can be quantified and compared against other algorithms are discussed. Finally, this chapter discusses various ways in which a particular implementation of an algorithm can be validated.

- Chapter 2, Data Structures Used in Algorithms, focuses on algorithms' need for necessary inmemory data structures that can hold the temporary data. Algorithms can be dataintensive, compute-intensive, or both. But for all different types of algorithms, choosing the right data structures is essential for their optimal implementation. Many algorithms have recursive and iterative logic and require specialized data structures that are fundamentally iterative in nature. As we are using Python in this book, this chapter focuses on Python data structures that can be used to implement the algorithms discussed in this book.

- Chapter 3, Sorting and Searching Algorithms, presents core algorithms that are used for sorting and searching. These algorithms can later become the basis for more complex algorithms. The chapter starts by presenting different types of sorting algorithms. It also compares the performance of various approaches. Then, various algorithms for searching are presented. They are compared and their performance and complexity are quantified. Finally, this chapter presents the actual applications of these algorithms.

- Chapter 4, Designing Algorithms, presents the core design concepts of various algorithms. It also explains different types of algorithms and discusses their strengths and weaknesses. Understanding these concepts is important when it comes to designing optimal complex algorithms. The chapter starts by discussing different types of algorithmic designs. Then, it presents the solution for the famous traveling salesman problem. It then discusses linear programming and its limitations. Finally, it presents a practical example that shows how linear programming can be used for capacity planning.

- Chapter 5, Graph Algorithms, focuses on the algorithms for graph problems that are common in computer science. There are many computational problems that can best be represented in terms of graphs. This chapter presents methods for representing a graph and for searching a graph. Searching a graph means systematically following the edges of the graph so as to visit the vertices of the graph. A graph-searching algorithm can discover a lot about the structure of a graph. Many algorithms begin by searching their input graph to obtain this structural information. Several other graph algorithms elaborate on basic graph searching. Techniques for searching a graph lie at the heart of the field of graph algorithms. The first section discusses the two most common computational representations of graphs: as adjacency lists and as adjacency matrices. Next, a simple graph-searching algorithm called breadth-first search is presented and shows how to create a breadth-first tree. The following section presents the depth-first search and provides some standard results about the order in which a depth-first search visits vertices.

- Chapter 6, Unsupervised Machine Learning Algorithms, introduces unsupervised machine learning algorithms. These algorithms are classified as unsupervised because the model or algorithm tries to learn inherent structures, patterns, and relationships from given data without any supervision. First, clustering methods are discussed. These are machine learning methods that try to find patterns of similarity and relationships among data samples in our dataset and then cluster these samples into various groups, such that each group or cluster of data samples has some similarity, based on the inherent attributes or features. The following section discusses dimensionality reduction algorithms, which are used when we end up having a number of features. Next, some algorithms that deal with anomaly detection are presented. Finally, this chapter presents association rule-mining, which is a data mining method used to examine and analyze large transactional datasets to identify patterns and rules of interest. These patterns represent interesting relationships and associations, among various items across transactions.

- Chapter 7, Traditional Supervised Learning Algorithms, describes traditional supervised machine learning algorithms in relation to a set of machine learning problems in which there is a labeled dataset with input attributes and corresponding output labels or classes. These inputs and corresponding outputs are then used to learn a generalized system, which can be used to predict results for previously unseen data points. First, the concept of classification is introduced in the context of machine learning. Then, the simplest of the machine learning algorithms, linear regression, is presented. This is followed by one of the most important algorithms, the decision tree. The limitations and strengths of decision tree algorithms are discussed, followed by two important algorithms, SVM and XGBoost.

- Chapter 8, Neural Network Algorithms, first introduces the main concepts and components of a typical neural network, which is becoming the most important type of machine learning technique. Then, it presents the various types of neural networks and also explains the various kinds of activation functions that are used to realize these neural networks. The backpropagation algorithm is then discussed in detail. This is the most widely used algorithm to converge the neural network problem. Next, the transfer learning technique is explained, which can be used to greatly simplify and partially automate the training of models. Finally, how to use deep learning to detect objects in multimedia data is presented as a real-world example.

- Chapter 9, Algorithms for Natural Language Processing, presents algorithms for natural language processing (NLP). This chapter proceeds from the theoretical to the practical in a progressive manner. First, it presents the fundamentals, followed by the underlying mathematics. Then, it discusses one of the most widely used neural networks to design and implement a couple of important use cases for textual data. The limitations of NLP are also discussed. Finally, a case study is presented where a model is trained to detect the author of a paper based on the writing style.

- Chapter 10, Recommendation Engines, focuses on recommendation engines, which are a way of modeling information available in relation to user preferences and then using this information to provide informed recommendations on the basis of that information. The basis of the recommendation engine is always the recorded interaction between the users and products. This chapter begins by presenting the basic idea behind recommendation engines. Then, it discusses various types of recommendation engines. Finally, this chapter discusses how recommendation engines are used to suggest items and products to different users.

- Chapter 11, Data Algorithms, focuses on the issues related to data-centric algorithms. The chapter starts with a brief overview of the issues related to data. Then, the criteria for classifying data are presented. Next, a description of how to apply algorithms to streaming data applications is provided and then the topic of cryptography is presented. Finally, a practical example of extracting patterns from Twitter data is presented.

- Chapter 12, Cryptography, introduces the algorithms related to cryptography. The chapter starts by presenting the background. Then, symmetrical encryption algorithms are discussed. MD5 and SHA hashing algorithms are explained and the limitations and weaknesses associated with implementing symmetric algorithms are presented. Next, asymmetric encryption algorithms are discussed and how they are used to create digital certificates. Finally, a practical example that summarizes all these techniques is discussed.

- Chapter 13, Large-Scale Algorithms, explains how large-scale algorithms handle data that cannot fit into the memory of a single node and involve processing that requires multiple CPUs. This chapter starts by discussing what types of algorithms are best suited to be run in parallel. Then, it discusses the issues related to parallelizing the algorithms. It also presents the CUDA architecture and discusses how a single GPU or an array of GPUs can be used to accelerate the algorithms and what changes need to be made to the algorithm in order to effectively utilize the power of the GPU. Finally, this chapter discusses cluster computing and discusses how Apache Spark creates resilient distributed datasets (RDDs) to create an extremely fast parallel implementation of standard algorithms.

- Chapter 14, Practical Considerations, starts with the important topic of explainability, which is becoming more and more important now that the logic behind automated decision making has been explained. Then, this chapter presents the ethics of using an algorithm and the possibilities of creating biases when implementing them. Next, the techniques for handling NP-hard problems are discussed in detail. Finally, ways to implement algorithms, and the real-world challenges associated with this, are summarized.