8 min read Why Sorting Algorithms Still Matter in Interviews Interviewers at top tech companies still ask about sorting not to test memorization, […] Read article
6 min read Core Entities Provider: provider_id, name, email, type (DOCTOR, THERAPIST, CONSULTANT, TUTOR), timezone, settings (JSONB: buffer_minutes_between_appointments, max_advance_days, min_notice_hours, auto_confirm). Schedule: schedule_id, Read article
6 min read 2D Grid BFS and DFS Fundamentals from collections import deque DIRS = [(0,1),(0,-1),(1,0),(-1,0)] # right, left, down, up def bfs_grid(grid, Read article
6 min read Cycle Detection in Undirected Graphs from collections import deque # DFS approach: track parent to distinguish back edge from tree Read article
6 min read Core Entities Product: product_id, sku, name, category_id, unit_cost, unit_weight_grams, dimensions (JSONB: length, width, height in mm), reorder_point, reorder_quantity, lead_time_days, is_active. Read article
6 min read 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] Read article
6 min read 1D DP Space Optimization # Fibonacci: O(n) -> O(1) space def fib(n: int) -> int: if n <= 1: return Read article
5 min read What is a Knowledge Graph? A knowledge graph stores entities (nodes) and typed relationships (edges) between them. Examples: Google Knowledge Read article
6 min read 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, Read article
6 min read Dijkstra’s Algorithm – Shortest Path (Non-negative Weights) import heapq from collections import defaultdict def dijkstra(graph: dict, start: int, n: int) Read article
5 min read Requirements and Scale Functional: shorten long URLs, redirect short URLs to originals, track click analytics (count, geography, device, referrer), support Read article
4 min read Heap Fundamentals A heap is a complete binary tree where every parent satisfies the heap property (min-heap: parent = children). Read article
6 min read Recursion Fundamentals Every recursive solution has: a base case (stops the recursion), a recursive case (reduces the problem), and a Read article
7 min read Core Entities Cart: cart_id, user_id (NULL for guest), session_id (for guest carts), status (ACTIVE, ABANDONED, CHECKED_OUT), currency, created_at, updated_at, expires_at. Read article
6 min read Geospatial Data Fundamentals Geospatial queries are common in production systems: “find the 10 nearest restaurants,” “is this user inside a Read article
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