1582 articles
LeetCode 268 hides four distinct valid solutions behind a deceptively simple problem. Learn Sort, HashSet, Gauss Formula, and XOR — understand exactly why each exists, when interviewers ask for each one, and why XOR is the most elegant answer in the room.
The Boyer-Moore Voting Algorithm solves LeetCode 169 in O(n) time and O(1) space using a brilliantly counterintuitive cancellation trick. Learn the proof, the dry run, all four approaches, and why interviewers love this problem — plus the Majority Element II follow-up that extends the same idea to two candidates.
LeetCode 448 is the definitive interview test for index-as-a-hash-key thinking. Learn the O(n) time, O(1) space negation trick that eliminates the need for any extra data structure — and every follow-up question a FAANG interviewer will throw at you after you solve it.
Given a binary array and an integer k, find the longest run of 1s you can create by flipping at most k zeros. Master the variable sliding window pattern that solves this in O(n) time and O(1) space — and learn the follow-up questions Google and Meta actually ask after you get it right.
Master LeetCode 414 — Third Maximum Number. Learn the subtle INT_MIN sentinel trap, two clean approaches (sorted set + three-variable O(1)), and real FAANG follow-up questions interviewers ask after you solve it.