1582 articles
Master Dijkstra's Dutch National Flag algorithm to sort 0s, 1s, and 2s in a single pass with O(1) space. Understand the three-pointer invariants, the critical bug most candidates make, and how this pattern unlocks a family of partition problems.
Master LeetCode 57 with the three-phase sweep algorithm. Learn exactly how to insert and merge intervals in O(n) time — a pattern that appears repeatedly at Google, Amazon, and Meta.
Master LeetCode 435 with the greedy earliest-end-time strategy. Learn why sorting by end time is the key insight, walk through a visual dry run, and ace every FAANG follow-up on interval scheduling.
Master LeetCode 39 — Combination Sum by understanding the backtracking decision tree, why unlimited reuse is handled by staying at the same index, and how sorting enables early pruning. Includes Python and JavaScript solutions with line-by-line comments, a full visual dry run, common mistakes, and follow-up questions on LC 40, LC 216, and LC 377.
LC 46 — Permutations is the canonical backtracking problem every interviewer uses to test recursive thinking. Learn two clean approaches — the visited-array method and the in-place swap method — with a full decision-tree dry run for [1,2,3], the three most common interview mistakes, and real follow-up questions on LC 47 and LC 60.