Data Structures & Algorithms

Array

Fixed-size, contiguous block of memory storing elements of the same type; O(1) access by index

Linked List

Sequence of nodes where each points to the next; O(1) insert/delete at head, O(n) search

Stack

LIFO (Last In, First Out) data structure; push and pop operations; O(1)

Queue

FIFO (First In, First Out) data structure; enqueue and dequeue operations; O(1)

Hash Table

Key-value store using hash function; average O(1) lookup, insert, delete

Binary Tree

Tree where each node has at most two children (left and right)

Binary Search Tree

Binary tree where left child < parent < right child; O(log n) average search

Heap

Complete binary tree; min-heap: parent ≤ children; used for priority queues

Graph

Set of vertices (nodes) connected by edges; can be directed or undirected

Big O Notation

Describes worst-case time/space complexity as input grows; e.g., O(n), O(log n)