Advanced Bit Manipulation Interview Patterns: XOR Tricks, Bitmask Subsets, and Bit DP (2025)
Core Bit Operations Reference # Fundamental bit tricks n & (n-1) # clear lowest set bit (check power of 2: […]
Algorithms
System Design
Low-Level Design: IT Ticketing System — Ticket Lifecycle, SLA Tracking, and Assignment (2025)
Core Entities Ticket: ticket_id, title, description, status (OPEN, IN_PROGRESS, PENDING, RESOLVED, CLOSED), priority (P1/P2/P3/P4), category (BUG, FEATURE, INCIDENT, QUESTION, CHANGE),
Algorithms
String Search Algorithm Interview Patterns: KMP, Rabin-Karp, Z-Algorithm, and Rolling Hash (2025)
Naive String Search and Why to Avoid It Naive string search: for each position i in text (0..n-m), compare pattern[0..m-1]
System Design
System Design: Live Sports Score Platform — Real-Time Updates, Fan Scale, and Stats (2025)
Requirements and Scale Functional: real-time score updates ( millions of simultaneous reads). Read-to-write ratio: 100,000:1. The core challenge is fan-side
Algorithms
Segment Tree and Fenwick Tree Interview Patterns: Range Queries, Lazy Propagation, and BIT (2025)
Binary Indexed Tree (Fenwick Tree / BIT) A BIT supports prefix sum queries and point updates in O(log n) time
Algorithms
Dynamic Programming Optimization Patterns: Space Reduction, Bitmask DP, and Interval DP (2025)
1D DP Space Optimization # Fibonacci: O(n) -> O(1) space def fib(n: int) -> int: if n int: prev2 =
System Design
System Design: Knowledge Graph — Entity Storage, Relationship Traversal, and Semantic Search (2025)
What is a Knowledge Graph? A knowledge graph stores entities (nodes) and typed relationships (edges) between them. Examples: Google Knowledge
System Design
Low-Level Design: Time Tracking System — Entries, Projects, Invoicing, and Reports
Core Entities User: user_id, name, email, role (EMPLOYEE, MANAGER, ADMIN), hourly_rate (default), timezone, created_at. Project: project_id, name, client_id, status (ACTIVE,
Algorithms
Advanced Graph Algorithm Interview Patterns: Dijkstra, Bellman-Ford, Topological Sort, and SCC (2025)
Dijkstra’s Algorithm – Shortest Path (Non-negative Weights) import heapq from collections import defaultdict def dijkstra(graph: dict, start: int, n: int)
System Design
System Design: URL Shortener and Click Analytics Platform (2025)
Requirements and Scale Functional: shorten long URLs, redirect short URLs to originals, track click analytics (count, geography, device, referrer), support
System Design
Low-Level Design: Survey Builder — Dynamic Forms, Response Collection, and Analytics
Core Entities Survey: survey_id, creator_id, title, description, status (DRAFT, ACTIVE, PAUSED, CLOSED), settings (JSONB: allow_anonymous, one_response_per_user, show_progress_bar, randomize_questions, response_limit), start_date,
Algorithms
Heap and Priority Queue Interview Patterns: K-th Largest, Merge Streams, and Scheduling (2025)
Heap Fundamentals A heap is a complete binary tree where every parent satisfies the heap property (min-heap: parent = children).
Algorithms
Math and Number Theory Interview Patterns: GCD, Primes, Modular Arithmetic, and Combinatorics (2025)
GCD, LCM, and Euclidean Algorithm import math def gcd(a: int, b: int) -> int: while b: a, b = b,
System Design
Low-Level Design: Poll and Voting System — Real-Time Results, Fraud Prevention, and Analytics
Core Entities Poll: poll_id, creator_id, question, poll_type (SINGLE_CHOICE, MULTIPLE_CHOICE, RANKED, RATING), status (DRAFT, ACTIVE, CLOSED), is_anonymous, allow_change_vote, visibility (PUBLIC, PRIVATE,
Algorithms
String Manipulation Interview Patterns: Anagrams, Palindromes, and Substring Problems (2025)
String Fundamentals for Interviews Strings are immutable in Python and Java — concatenating in a loop is O(n^2). Use a