6 linear data structures for every software engineer

Understanding data structures is important for every software engineer. They are the building blocks of efficient and scalable software.

Whether you’re sorting data, managing databases, or optimizing algorithms, knowing the right data structure can make all the difference. Let’s explore data structures in-depth and see why they’re so important.

What is a data structure?#

A data structure is a way of organizing and storing data so that it can be accessed and modified efficiently. Just think of it as a container that holds your data in a specific layout. There are many types of data structures, each with its own strengths and use cases. Some are simple and linear, like arrays and linked lists, while others are more complex, like trees and graphs.

Why do we need data structures?#

In software development, mastering data structures is key to managing and processing data efficiently. Here’s why

1. Efficiency: Using the right data structure can significantly reduce the time complexity of your algorithms. For example, searching for an item in an unsorted array takes linear time $O(n)$, but using a binary search tree can reduce this to logarithmic time $O(\text{log}(n))$.

2. Memory management: Data structures help in organizing data in memory. For instance, a hash table can efficiently manage a large set of data by using a hash function to distribute data evenly across an array.

3. Real-world applications: From databases to network routing algorithms, data structures are used everywhere. For example, social media platforms use graph data structures to represent and analyze user connections.

By understanding and implementing the right data structure, you can make your software faster, more efficient, and easier to manage. This knowledge is crucial for tackling more complex problems in your software engineering career.

6 linear data structures #

A linear data structure is a type of data structure where elements are arranged sequentially or in a linear order.

Let’s first list the top 6 linear data structures and take a deep dive into each one by one:

1. Arrays

2. Strings

3. Linked lists

4. Stacks

5. Queues

6. Hash table

Each of the above data structures has unique properties and advantages that make them suitable for different tasks. In the following sections, we will explore each one, discussing their concepts, operations, advantages, and applications.

1. Arrays#

An array is a collection of elements stored at contiguous memory locations. It allows you to store multiple items of the same type together. It is easy to manage and access by using indexes. Arrays are a fundamental data structure in programming due to their simplicity and efficiency.

The following are the types of arrays:

• One-dimensional array: A single list of elements (as illustrated above).

• Two-dimensional array: A matrix or table of elements, often visualized as rows and columns.

• Multi-dimensional array: Arrays within arrays, useful for representing complex data structures.

Common operations:

• Insertion: Adds an element at a specific position in the array.

• Deletion: Removes an element from a specific position in the array.

• Searching: Finds the position of an element within the array.

Advantages and disadvantages#

Let’s discuss some advantages and disadvantages of arrays:

• Advantages:

  • Fast access: You can access any element in constant time, $O(1)$, using its index.

  • Memory efficiency: Arrays are stored in contiguous memory, which makes memory management easy for larger datasets.

• Disadvantages:

  • Fixed-size: Once an array is created, its size cannot be changed. This can lead to wasted memory if the array is underutilized or the need for resizing if it is overutilized.

  • Costly operations: Inserting or deleting elements, especially in the middle of an array, can be costly as it requires shifting other elements.

Commonly asked interview problems of arrays#

Now, let’s look at some commonly asked interview problems of arrays. You can click the problem titles in the following illustration to see more details and attempt the exercise.

2. Strings#

A string is a sequence of characters used to represent text. It is one of the most commonly used data structures in programming. It can include letters, numbers, and symbols and is typically stored as a null-terminated array of characters.

Common operations:

• Concatenation: Combines two or more strings into one.

• Substring: Extracts a part of a string.

• Searching: Finds the position of a substring within a string.

• Pattern matching: Uses regular expressions to find or manipulate parts of a string that match a certain pattern.

Advantages and disadvantages#

Let’s discuss some advantages and disadvantages of strings:

• Advantages:

  • Ease of use: Strings are simple to use for representing and manipulating text.

  • Human-readable: Strings are easy to read and write, making them ideal for storing and displaying text.

• Disadvantages:

  • Immutability: In many languages, strings are immutable, meaning that every modification creates a new string. This can lead to inefficiency if not handled properly.

  • Memory usage: Large strings or frequent modifications can consume significant memory, especially in languages with immutable strings.

Commonly asked interview problems of strings#

Now, let’s look at some commonly asked interview problems of strings. You can click the problem titles in the following illustration to see more details and attempt the exercise.

3. Linked lists#

A linked list is a data structure consisting of nodes containing data and a reference (or link) to the immediate next node in sequence. Unlike arrays, linked lists do not store elements in contiguous memory locations, which allows dynamic memory allocation.

The following are the types of linked lists:

• Singly linked list: It is unidirectional, where each node contains data and a reference to the next node.

• Doubly linked list: It is bidirectional, where each node contains data, a reference to the next node, and a reference to the previous node as well.

• Circular linked list: It is a linked list, where the last node points back to the first node, forming a circle.

Common operations:

• Insertion: Adds a node to the linked list at the beginning, end, or a specific position.

• Deletion: Removes a node from the beginning, end, or a specific position.

• Traversal: Visits each node in the linked list to access or modify data.

Advantages and disadvantages#

Let’s discuss some advantages and disadvantages of the strings:

• Advantages:

  • Dynamic size: Linked lists can grow or shrink in size as needed, making them flexible in terms of memory usage.

  • Efficient insertions/deletions: Inserting or deleting nodes can be done efficiently without shifting elements, unlike arrays.

• Disadvantages:

  • Extra memory overhead: Each node requires additional memory for storing pointers, which can add overhead.

  • Sequential access: Unlike arrays, linked lists do not provide constant time $O(1)$ access to elements by index, requiring traversal from the head node.

Commonly asked interview problems of linked lists#

Now, let’s look at some commonly asked interview problems of linked lists. You can click the problem titles in the following illustration to see more details and attempt the exercise.

4. Stacks#

A stack is a linear data structure that follows the Last In, First Out (LIFO) principle. This means that the last element added to the stack is the first one to be removed. Imagine a stack of plates, you add plates to the top and also remove plates from the top.

Common operations:

• Push: Adds an element to the top of the stack.

• Pop: Removes the top element from the stack.

• Peek: Views the top element without removing it.

Advantages and disadvantages#

Let’s discuss an advantage and disadvantage of stacks:

• Advantage:

  • Efficient operations: Push and pop operations are fast, with $O(1)$ time complexity.

• Disadvantage:

  • Limited access: You can only access the top element directly.

Commonly asked interview problems of stacks#

Now, let’s look at some commonly asked interview problems of stacks. You can click the problem titles in the following illustration to see more details and attempt the exercise.

5. Queues#

A queue is a linear data structure that follows the First In, First Out (FIFO) principle. This means that the first element added to the queue will be the first one to be removed. Think of a queue as a line of people waiting for service; the person who gets in line first is served first. When a new person arrives, they join the other end of the line.

The following are the types of queues:

• Basic queue: The basic type of queue where elements are added at the rear and removed from the front.

• Circular queue: A type of queue where the last position is connected back to the first position, forming a circle. This helps in efficiently utilizing the space.

• Priority queue: A special type of queue where each element is associated with a priority, and elements are removed based on their priority.

• Deque (double-ended queue): A type of queue where elements can be added or removed from both the front and rear ends.

Common operations:

• Enqueue: Adds an element to the rear of the queue.

• EnqueueFront: Inserts an element at the front of the deque.

• Dequeue: Removes an element from the front of the queue.

• DequeueRear: Removes an element from the rear of the deque.

• Front: Views the front element without removing it.

• Rear: Views the rear element without removing it.

Advantages and disadvantages#

Let’s discuss an advantage and a disadvantage of queues:

• Advantage:

  • Order preservation: Maintains the order of elements as they are added and removed.

• Disadvantage:

  • Limited access: Direct access to elements other than the front or rear is not possible.

Commonly asked interview problems of queues#

Now, let’s look at some commonly asked interview problems of queues. You can click the problem titles in the following illustration to see more details and attempt the exercise.

6. Hash table#

A hash table is a data structure that implements an associative array, a structure that can map keys to values. It uses a hash function to compute an index from which the desired value can be found.

Common operations:

• Insertion: Adds a key-value pair to the hash table.

• Deletion: Removes a key-value pair from the hash table.

• Searching: Retrieves the value associated with a given key.

Advantages and disadvantages#

Let’s discuss some advantages and disadvantages of hash tables:

• Advantages:

  • Fast access: Provides average-case time complexity of $O(1)$ for insertion, deletion, and search operations.

  • Efficient memory usage: Can be more memory efficient compared to other data structures like trees for certain applications.

• Disadvantages:

  • Collisions: Hash tables can suffer from collisions, which need to be handled efficiently to maintain performance.

  • Complexity in choosing hash functions: The performance of a hash table depends on the quality of the hash function and the load factor.

Commonly asked interview problems of hash table#

Now, let’s look at some commonly asked interview problems of hash tables. You can click the problem titles in the following illustration to see more details and attempt the exercise.

Become proficient in data structures#

In this blog, we explored the most important linear data structures that every software engineer should know. From arrays and linked lists to hash tables, each data structure has its unique properties and applications. By mastering these data structures, you’ll be better skilled to tackle a wide range of programming challenges and develop more efficient and effective software solutions in the future.

To become more proficient, consider experimenting with implementing different data structures and solving problems on our platform. The more you practice, the more intuitive and powerful your understanding of data structures will become. We have courses that get you hands-on with data structures in several languages below.

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