1582 articles
Eighteen advanced graph problems collapsed into one decision tree. Match the problem cue to the algorithm in seconds: MST, SCC, bridges, Floyd-Warshall, Bellman-Ford, A-star, topological sort, Eulerian paths, and max flow with complexity bounds you can quote on demand.
A complete pattern guide to arrays and strings problems from LeetCode used by Google, Meta, Amazon, Apple, and Microsoft. Covers prefix sum, Kadane, two pointers, sliding window, hash maps, and Dutch flag in Python and JavaScript.
LeetCode 1 — Two Sum is the most-asked Amazon, Google, and Meta phone screen warmup. Single-pass hash map gives O(n) time and unlocks the complement-lookup pattern.
LeetCode 121 — track the running minimum and the running best profit in a single linear pass. The cleanest greedy pattern asked at Amazon, Google, and Microsoft.
LeetCode 217 asks whether any value repeats in an array. The hash set answer runs in O(n) time and O(n) space. This guide compares it against sorting and brute force, shows why hash sets degrade to O(n) in the worst case, and works through the Contains Duplicate II and III follow-ups interviewers actually ask next.