Performance of a Data Structure

Why data structures matter

The fact is that programs are all about processing data. Data structures are referred to how data is organized which affects the time of executing a program.

How to measure the performance of a data structure

In order to measure "how fast"/efficiency/performance of a data structure, we measure the performance of its operations. There are four basic operations including reading, searching, insertion, and deletion. A pure time consuming is not used for the measuring because it is not reliable depending on the hardware that it is run on. But instead, we use the term time complexity which refers to how many steps an operation takes.

An example of how a single rule can affect efficiency

Let's compare two data structures: Array and Set (with N elements).

1. Array

- Reading: 1 step (because the computer has the ability to jump to any particular index in the array)
- Searching: N steps (the worst case with linear search)
- Insertion: N + 1 steps (the worst case inserting at index 0: N steps of right-shifts + 1 step of insertion)
- Deletion: N steps (the worst case deleting at index 0: N-1 steps of left-shifts + 1 step of deletion)

2. Set

- Reading: 1 step
- Searching: N steps
- Insertion: best case: N + 1 steps; worst case: 2N + 1 steps (every insert first requires a search)
- Deletion: N steps

NOTE: I mentioned the set by setting up from an array. There is another way to set up a set by a hash table.

Reference:

[1]. Jay Wengrow | A Common-Sense Guide to Data Structures and Algorithms: Level Up Your Core Programming Skills

Comments

Avoiding Time-Wasting Pitfalls in Agile Estimation

If you do Scrum at work, you might be very familiar to the estimation in Planning 1 . My PO has once complained to my team that why it took too long for estimating just a story. Wasting time results in the planning timebox is violated. I give you some advice from my experience: Estimation is estimation, not measure. When you read some requirements, you see some risks but you actually don't know how complicated it will be. Don't try to influence the others by explaining how to do it in too detail. Just keep in mind that you know the business domain pertaining to customer needs and estimate how much effort you will spend for it. The effort should be compared to your baseline one that you use for a simple requirement. The bottom line is we do "relative estimation", not absolute estimation. For example, you are asked to estimate the height of a building. Basically, you just need to answer "how many times higher is the build than your height"; you do...

Multiple Inheritance of State and Implementation

Today, I was just curious about why an enum can not extend anything else. I took a look on the Oracle document here , and I found the answer is below: "All enums implicitly extend java.lang.Enum. Because a class can only extend one parent (see Declaring Classes), the Java language does not support multiple inheritance of state (see Multiple Inheritance of State, Implementation, and Type), and therefore an enum cannot extend anything else." I have been learned of it before. But, wait a sec...! Why Java does not support multiple inheritance of state? Since I have worked with other programming languages like C++, I was able to make a class extend some other classes. The short answer is to avoid the issues of multiple inheritance of state . I wonder if other programming languages have these below terms but Java does. Multiple inheritance of state It is the ability to inherit fields from multiple classes. There is a problem and Java avoids it. "For exa...

Strategy Design Pattern

For example, I have a program with an Animal abstract class and two sub-classes Dog and Bird. I want to add new behavior for the class Animal, this is "fly". Now, I face two approaches to solve this issue: 1. Adding an abstract method "fly" into the class Animal. Then, I force the sub-classes should be implemented this method, something like: public abstract class Animal{ //bla bla public abstract void fly(); } public class Bird extends Animal{ //bla bla public void fly(){ System.out.println("Fly high"); } } public class Dog extends Animal{ //bla bla public void fly(){ System.out.println("Cant fly"); } } 2. Creating an interface with method "fly" inside. The same issue to an abstract class, I force the classes these implement this interface should have a method "fly" inside: public interface Flyable{ public void fly(); } public class Bird implements Flyable{ //bla bla public void fly(){ System.out.pr...

Math fundamentals and Katex

It was really tough for me to understand many articles about data science due to the requirements of understanding mathematics (especially linear algebra). I’ve started to gain some basic knowledges about Math by reading a book first. The great tool Typora and stackedit with supporting Katex syntax simply helps me to display Math-related symbols. Let’s start! The fundamental ideas of mathematics: “doing math” with numbers and functions. Linear algebra: “doing math” with vectors and linear transformations. 1. Solving equations Solving equations means finding the value of the unknown in the equation. To find the solution, we must break the problem down into simpler steps. E.g: x 2 − 4 = 4 5 x 2 − 4 + 4 = 4 5 + 4 x 2 = 4 9 x = 4 9 ∣ x ∣ = 7 x = 7 or x = − 7 \begin{aligned} x^2 - 4 &= 45\\ x^2 - 4 + 4 &= 45 + 4\\ x^2 &= 49\\ \sqrt{x}&=\sqrt{49}\\ |x| &= 7\\ x=7 &\text{ or } x=-7 \end{aligned} x 2 − 4 x 2 − 4 + 4 x 2 x ∣ x ∣ x = 7 = 4 5 = 4 ...

MS SQL Server Views

"Creates a virtual table whose contents (columns and rows) are defined by a query. Use this statement to create a view of the data in one or more tables in the database. For example, a view can be used for the following purposes: - To focus, simplify, and customize the perception each user has of the database. - As a security mechanism by allowing users to access data through the view, without granting the users permissions to directly access the underlying base tables. - To provide a backward compatible interface to emulate a table whose schema has changed." [1] Beside that, our team used view in order to improve the performance of our web apps when a database has a very complicated relationship between its tables by using ORM Frameworks such as Hibernate. Example code: --create CREATE VIEW placeholders AS SELECT EMPKEY AS empkey, CONNUMB AS connumb, EMPNBR AS empNbr, ACEEMPN AS empFirstName, ACEEMPFN AS empLastName, EMPNAM AS empFullName, ...

vhandit

Search This Blog