Data Structures Overview

Introduction

• Review of 7 important data structures
• Importance: coding interviews, computer science classes, building projects
• Order of explanation: easiest to hardest
• Simplified explanations with common uses
• Time complexity provided for reference

Arrays

• Definition: Ordered collections of data (integers, strings, etc.)
• Use Case: Storing temperature data for the next 5 days
• Advantages: Easy to find elements using indexes (zero-based indexing)
  • Fast read operations: O(1)
• Disadvantages: Slower insertion/deletion (O(n))
  • Stored in contiguous memory; reallocation required if space is insufficient

Linked Lists

• Definition: Store ordered lists of data elements with pointers to next elements
• Advantages: Fast insertion/deletion
  • Elements don't need to be stored contiguously; use pointers
• Disadvantages: Slower reading due to lack of indexes
  • Must traverse from the beginning to find an element

Hash Map

• Definition: Similar to arrays but indexed using custom keys (key-value pairs)
• Advantages: Fast operations (O(1)) for insert, delete, and search
  • Unordered data structure
  • Keys allow for quick searching (e.g., storing capital cities by country)
• Alternative Names: Hash tables, dictionaries (in Python)

Stacks & Queues

Stacks

• Concept: Stack of plates/pancakes (LIFO: last in, first out)
• Operations:
  • Push: Add element to the top
  • Pop: Remove top-most element
  • Peek: View top-most element
• Use Cases: Suitable for problems requiring LIFO structure

Queues

• Concept: Lineup at grocery store (FIFO: first in, first out)
• Operations:
  • Enqueue: Add element to the back
  • Dequeue: Remove front-most element
  • Front: View front-most element
• Use Cases: More frequently used; e.g., YouTube playlists

Trees

• Definition: Data structures resembling trees with nodes and edges
• Key Components: Root node, parent and child nodes, leaves
• Types: Binary trees, binary search trees
  • Binary Tree: Parent nodes have up to 2 children
  • Binary Search Tree: Left children < parent < right children
• Advantages: Efficiently search large ordered datasets (O(log n))
  • Example: Digital dictionary

Graphs

• Definition: Models for a set of connections
• Components: Nodes and edges
  • Less restrictive than trees, can have cycles, directed/undirected, weighted edges
• Complexity: Considered one of the hardest data structures
• Use Cases: Optimizing routes, e.g., Uber

Conclusion

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