Data structures are fundamental ways to organize and store data in computer memory for efficient access and modification. They are broadly classified into two main categories: Linear and Non-linear structures. Linear data structures include arrays, stacks, queues, and linked lists, where elements are arranged sequentially. Non-linear structures like trees and graphs allow more complex relationships between elements.
Now let's define the basic data structures. An Array is a collection of elements stored in contiguous memory locations, accessed by index. A Stack follows Last-In-First-Out principle with push and pop operations. A Queue follows First-In-First-Out principle with enqueue and dequeue operations. A Linked List consists of nodes containing data and pointers to the next node, allowing dynamic memory allocation.
Data structures are fundamentally divided into two categories: Primitive and Non-primitive. Primitive data structures are the basic building blocks like integers, floats, characters, and booleans. They have fixed sizes and provide direct memory access. Non-primitive data structures are more complex, built from primitive types. They include arrays, stacks, queues, trees, and graphs. These structures can have dynamic sizes and offer more sophisticated data organization capabilities.
Algorithm complexity analysis is crucial for understanding performance. Time complexity measures how execution time grows with input size, while space complexity measures memory usage growth. Big O notation provides the upper bound of growth rate, with common complexities like O(1) constant, O(n) linear, O(n squared) quadratic, and O(log n) logarithmic. We analyze three cases: best case showing minimum requirements, average case for typical inputs, and worst case showing maximum requirements.
Object-Oriented Programming organizes code using classes and objects. A Class is a blueprint that defines attributes and methods, while an Object is an actual instance of a class with specific values. Constructors are special methods that initialize objects when they are created. Methods include instance methods that operate on objects, class methods that belong to the class, and static methods that are independent. Abstract Data Types define operations without implementation details, providing a clean interface. Recursion functions call themselves with a base case to solve problems by breaking them into smaller subproblems.