The Best and Easiest Way to Understand an Algorithm
Reviewed and fact-checked by Sayantoni Das

What is an Algorithm?

An algorithm is a set of commands that must be followed for a computer to perform calculations or other problem-solving operations.According to its formal definition, an algorithm is a finite set of instructions carried out in a specific order to perform a particular task. It is not the entire program or code; it is simple logic to a problem represented as an informal description in the form of a flowchart or pseudocode.


  • Problem: A problem can be defined as a real-world problem or real-world instance problem for which you need to develop a program or set of instructions. An algorithm is a set of instructions. 
  • Algorithm: An algorithm is defined as a step-by-step process that will be designed for a problem.
  • Input: After designing an algorithm, the algorithm is given the necessary and desired inputs.
  • Processing unit: The input will be passed to the processing unit, producing the desired output.
  • Output: The outcome or result of the program is referred to as the output.

After defining what an algorithm is, you will now look at algorithm characteristics.

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How do Algorithms Work?

Algorithms are step-by-step procedures designed to solve specific problems and perform tasks efficiently in the realm of computer science and mathematics. These powerful sets of instructions form the backbone of modern technology and govern everything from web searches to artificial intelligence. Here's how algorithms work:

  • Input: Algorithms take input data, which can be in various formats, such as numbers, text, or images.

  • Processing: The algorithm processes the input data through a series of logical and mathematical operations, manipulating and transforming it as needed.

  • Output: After the processing is complete, the algorithm produces an output, which could be a result, a decision, or some other meaningful information.

  • Efficiency: A key aspect of algorithms is their efficiency, aiming to accomplish tasks quickly and with minimal resources.

  • Optimization: Algorithm designers constantly seek ways to optimize their algorithms, making them faster and more reliable.

  • Implementation: Algorithms are implemented in various programming languages, enabling computers to execute them and produce desired outcomes.

What is the Need for Algorithms?

You require algorithms for the following reasons:


It aids in your understanding of scalability. When you have a sizable real-world problem, you must break it down into small steps to analyze it quickly.


The real world is challenging to break down into smaller steps. If a problem can be easily divided into smaller steps, it indicates that the problem is feasible.

After understanding what is an algorithm, why you need an algorithm, you will look at how to write one using an example.

Types of Algorithms

  1. Brute Force Algorithm: A straightforward approach that exhaustively tries all possible solutions, suitable for small problem instances but may become impractical for larger ones due to its high time complexity.

  2. Recursive Algorithm: A method that breaks a problem into smaller, similar subproblems and repeatedly applies itself to solve them until reaching a base case, making it effective for tasks with recursive structures.

  3. Encryption Algorithm: Utilized to transform data into a secure, unreadable form using cryptographic techniques, ensuring confidentiality and privacy in digital communications and transactions.

  4. Backtracking Algorithm: A trial-and-error technique used to explore potential solutions by undoing choices when they lead to an incorrect outcome, commonly employed in puzzles and optimization problems.

  5. Searching Algorithm: Designed to find a specific target within a dataset, enabling efficient retrieval of information from sorted or unsorted collections.

  6. Sorting Algorithm: Aimed at arranging elements in a specific order, like numerical or alphabetical, to enhance data organization and retrieval.

  7. Hashing Algorithm: Converts data into a fixed-size hash value, enabling rapid data access and retrieval in hash tables, commonly used in databases and password storage.

  8. Divide and Conquer Algorithm: Breaks a complex problem into smaller subproblems, solves them independently, and then combines their solutions to address the original problem effectively.

  9. Greedy Algorithm: Makes locally optimal choices at each step in the hope of finding a global optimum, useful for optimization problems but may not always lead to the best solution.

  10. Dynamic Programming Algorithm: Stores and reuses intermediate results to avoid redundant computations, enhancing the efficiency of solving complex problems.

  11. Randomized Algorithm: Utilizes randomness in its steps to achieve a solution, often used in situations where an approximate or probabilistic answer suffices.

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How to Write an Algorithm?

  • There are no well-defined standards for writing algorithms. It is, however, a problem that is resource-dependent. Algorithms are never written with a specific programming language in mind.
  • As you all know, basic code constructs such as loops like do, for, while, all programming languages share flow control such as if-else, and so on. An algorithm can be written using these common constructs.
  • Algorithms are typically written in a step-by-step fashion, but this is not always the case. Algorithm writing is a process that occurs after the problem domain has been well-defined. That is, you must be aware of the problem domain for which you are developing a solution.


Now, use an example to learn how to write algorithms.

Problem: Create an algorithm that multiplies two numbers and displays the output.

Step 1 − Start

Step 2 − declare three integers x, y & z

Step 3 − define values of x & y

Step 4 − multiply values of x & y

Step 5 − store result of step 4 to z

Step 6 − print z

Step 7 − Stop

Algorithms instruct programmers on how to write code. In addition, the algorithm can be written as:

Step 1 − Start mul

Step 2 − get values of x & y

Step 3 − z ← x * y

Step 4 − display z

Step 5 − Stop

In algorithm design and analysis, the second method is typically used to describe an algorithm. It allows the analyst to analyze the algorithm while ignoring all unwanted definitions easily. They can see which operations are being used and how the process is progressing. It is optional to write step numbers. To solve a given problem, you create an algorithm. A problem can be solved in a variety of ways.


As a result, many solution algorithms for a given problem can be derived. The following step is to evaluate the proposed solution algorithms and implement the most appropriate solution.

As you progress through this "what is an Algorithm" tutorial, you will learn about some of the components of an algorithm.

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Factors of an Algorithm

The following are the factors to consider when designing an algorithm:

  • Modularity: This feature was perfectly designed for the algorithm if you are given a problem and break it down into small-small modules or small-small steps, which is a basic definition of an algorithm.
  • Correctness: An algorithm's correctness is defined as when the given inputs produce the desired output, indicating that the algorithm was designed correctly. An algorithm's analysis has been completed correctly.
  • Maintainability: It means that the algorithm should be designed in a straightforward, structured way so that when you redefine the algorithm, no significant changes are made to the algorithm.
  • Functionality: It takes into account various logical steps to solve a real-world problem.
  • Robustness: Robustness refers to an algorithm's ability to define your problem clearly.
  • User-friendly: If the algorithm is difficult to understand, the designer will not explain it to the programmer.
  • Simplicity: If an algorithm is simple, it is simple to understand.
  • Extensibility: Your algorithm should be extensible if another algorithm designer or programmer wants to use it.

You will now see why an algorithm is so essential after understanding some of its components.

Qualities of a Good Algorithm

  • Efficiency: A good algorithm should perform its task quickly and use minimal resources.
  • Correctness: It must produce the correct and accurate output for all valid inputs.
  • Clarity: The algorithm should be easy to understand and comprehend, making it maintainable and modifiable.
  • Scalability: It should handle larger data sets and problem sizes without a significant decrease in performance.
  • Reliability: The algorithm should consistently deliver correct results under different conditions and environments.
  • Optimality: Striving for the most efficient solution within the given problem constraints.
  • Robustness: Capable of handling unexpected inputs or errors gracefully without crashing.
  • Adaptability: Ideally, it can be applied to a range of related problems with minimal adjustments.
  • Simplicity: Keeping the algorithm as simple as possible while meeting its requirements, avoiding unnecessary complexity.

The Complexity of an Algorithm

The algorithm's performance can be measured in two ways:

Time Complexity

The amount of time required to complete an algorithm's execution is called time complexity. The big O notation is used to represent an algorithm's time complexity. The asymptotic notation for describing time complexity, in this case, is big O notation. The time complexity is calculated primarily by counting the number of steps required to complete the execution. Let us look at an example of time complexity.

mul = 1;

// Suppose you have to calculate the multiplication of n numbers.  

for i=1 to n  

mul = mul *1;  

// when the loop ends, then mul holds the multiplication of the n numbers  

return mul;  

The time complexity of the loop statement in the preceding code is at least n, and as the value of n escalates, so does the time complexity. While the code's complexity, i.e., returns mul, will be constant because its value is not dependent on the importance of n and will provide the result in a single step. The worst-time complexity is generally considered because it is the maximum time required for any given input size.

Space Complexity

The amount of space an algorithm requires to solve a problem and produce an output is called its space complexity. Space complexity, like time complexity, is expressed in big O notation.

The space is required for an algorithm for the following reasons:

  1. To store program instructions.
  2. To store track of constant values.
  3. To store track of variable values.
  4. To store track of function calls, jumping statements, and so on.

Space Complexity = Auxiliary Space + Input Size

Finally after understanding what is an algorithm, its analysis and approches, you will look at different types of algorithms.

Advantage and Disadvantages of Algorithms

Advantages of Algorithms:

  • Efficiency: Algorithms streamline processes, leading to faster and more optimized solutions.
  • Reproducibility: They yield consistent results when provided with the same inputs.
  • Problem-solving: Algorithms offer systematic approaches to tackle complex problems effectively.
  • Scalability: Many algorithms can handle larger datasets and scale with increasing input sizes.
  • Automation: They enable automation of tasks, reducing the need for manual intervention.

Disadvantages of Algorithms:

  • Complexity: Developing sophisticated algorithms can be challenging and time-consuming.
  • Limitations: Some problems may not have efficient algorithms, leading to suboptimal solutions.
  • Resource Intensive: Certain algorithms may require significant computational resources.
  • Inaccuracy: Inappropriate algorithm design or implementation can result in incorrect outputs.
  • Maintenance: As technology evolves, algorithms may require updates to stay relevant and effective.

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Next Steps

In this tutorial, you learned what an algorithm is and what its characteristics are. After that, you took a look at why you need algorithms, how to write them, and how important they are. After you learned about the approaches and factors of an algorithm, you learned about complexity and types of algorithms.

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Do you have any questions about this tutorial on what an algorithm is? If you do, please leave them in the comments section at the bottom of this page. Our specialists will respond to your questions as quickly as possible!

About the Author

Soni UpadhyaySoni Upadhyay

Soni Upadhyay is with Simplilearn's Research Analysis Team. She's a Computer Science and Engineering graduate. Programming languages are her area of expertise. She has a brilliant knowledge of C, C++, and Java Programming languages

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