Book Image

Hands-On Data Structures and Algorithms with Python – Third Edition - Third Edition

By : Dr. Basant Agarwal
Book Image

Hands-On Data Structures and Algorithms with Python – Third Edition - Third Edition

By: Dr. Basant Agarwal

Overview of this book

Choosing the right data structure is pivotal to optimizing the performance and scalability of applications. This new edition of Hands-On Data Structures and Algorithms with Python will expand your understanding of key structures, including stacks, queues, and lists, and also show you how to apply priority queues and heaps in applications. You’ll learn how to analyze and compare Python algorithms, and understand which algorithms should be used for a problem based on running time and computational complexity. You will also become confident organizing your code in a manageable, consistent, and scalable way, which will boost your productivity as a Python developer. By the end of this Python book, you’ll be able to manipulate the most important data structures and algorithms to more efficiently store, organize, and access data in your applications.
Table of Contents (17 chapters)
14
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15
Index

Chapter 12: Selection Algorithm

Question 1

What will be the output if the quickselect algorithm is applied to the given array arr=[3, 1, 10, 4, 6, 5] with k given as 2?

Solution

  1. Given the initial array: [3, 1, 10, 4, 6, 5], we can find the median of medians: 4 (index = 3).
  2. We swap the pivot element with the first element: [4, 1, 3, 10, 6, 5].
  3. We will move the pivot element to its correct position: [1, 3, 4, 10, 6, 5].
  4. Now we get a split index equal to 2 but the value of k is also equal to 2, hence the value at index 2 will be our output. Hence the output will be 4.

Question 2

Can quickselect find the smallest element in an array with duplicate values?

Solution

Yes, it works. By the end of every iteration, we have all elements less than the current pivot stored to the left of the pivot. Let’s consider when all elements are the same. In this case, every iteration ends up putting a pivot element to the left of the array...