1582 articles
LeetCode 344 is the canonical two-pointer problem — and it shows up at Meta, Microsoft, and Amazon as both a standalone question and as the foundation for palindrome checks, anagram detection, and rotate-array problems. Learn the in-place swap pattern deeply, trace through every edge case, and master the follow-ups that separate passing candidates from standout ones.
LeetCode 387 is deceptively simple — but the way you solve it, explain it, and handle its follow-ups separates candidates who get the offer from those who do not. Master the two-pass frequency map, understand why O(1) space is possible, and be ready for every streaming and ordering twist Amazon throws at you.
Master LeetCode 125 — Valid Palindrome with the O(1)-space two-pointer technique. Learn why every FAANG loop starts here, visualize the pointer walk on a classic example, avoid the four most common pitfalls, and unlock the palindrome follow-up chain: LC 680, LC 5, and LC 647.
LeetCode 14 appears deceptively simple — until the interviewer asks you to do it without sorting, then with binary search, then on a stream of words. Master all three approaches (vertical scan, horizontal fold, binary search on length), understand exactly why each one works, and walk into your Google screen ready for every escalation.
Count primes below n sounds trivial — until your naive solution times out on n=5,000,000. Master the Sieve of Eratosthenes, one of the most elegant algorithms in all of computer science, and learn the exact intuition that separates candidates who pass Amazon and Google screens from those who do not.