Algorithms

⏱ 7 min read Segment Tree A segment tree answers range queries (range sum, range minimum) in O(log n) and supports point or range […] Read article

⏱ 6 min read When to Use 2D DP 2D DP uses a table dp[i][j] where i and j represent positions in two sequences, Read article

⏱ 5 min read The Sliding Window Technique for Strings A sliding window maintains a contiguous substring without re-scanning from scratch. Two pointers (left Read article

⏱ 6 min read Why Sorting Matters in Interviews Sorting is foundational: dozens of problems become O(n log n) after sorting (two-sum, 3-sum, interval Read article

⏱ 5 min read Matrix as a Graph A 2D matrix is an implicit graph where each cell (r, c) is a node connected Read article

⏱ 5 min read Interval Problems: Core Insight Interval problems involve ranges [start, end]. The key operations: merge overlapping intervals, find non-overlapping sets, detect Read article

⏱ 5 min read Prefix Sum Interview Patterns Prefix sums transform range sum queries from O(n) to O(1) after O(n) preprocessing. They also underlie Read article

⏱ 5 min read Interval Problem Fundamentals Interval problems involve ranges [start, end] and ask about overlaps, merges, insertions, or optimal scheduling. The key Read article

⏱ 7 min read The 0/1 Knapsack Pattern The 0/1 Knapsack problem is one of the most important DP patterns — its structure appears Read article

⏱ 6 min read Union-Find (Disjoint Set Union) Interview Patterns Union-Find (DSU) solves the dynamic connectivity problem: given a graph where edges are added Read article

⏱ 6 min read Interval Algorithm Patterns Interval problems appear constantly in coding interviews — at Google, Meta, Airbnb, and Uber. The key skill: Read article

⏱ 6 min read Dynamic Programming on Strings String DP problems are among the most common in technical interviews, especially at Meta, Amazon, and Read article

⏱ 9 min read Low-Level Design: Food Delivery System (OOP Interview) The food delivery system (DoorDash/Uber Eats style) is a rich OOP design problem Read article

⏱ 8 min read Low-Level Design: Chat Application (OOP Interview) A chat application combines real-time messaging, user management, conversation threading, and notification delivery. It’s Read article

⏱ 9 min read Graph Traversal Interview Patterns (2025) Graph problems are among the most common in FAANG interviews — they appear as network Read article