CONCEPT BLOGS
Multi-phase guides with mental models, worked examples, diagrams, and real edge cases — the public form of Learnisim AI's conceptual learning. Read here; train it interactively in the app.
![2 closest of [[1,3],[-2,2],[2,-2]] overview diagram](/blogs/k-closest-points-to-origin-explained-1-3-2-2-2-2-walkthrough/diagrams/hero.svg)
Learn how to find the K closest points to the origin by tracing [[1,3],[-2,2],[2,-2]] with a geometric distance mental model.
![2nd largest in [3, 2, 1, 5, 6, 4] overview diagram](/blogs/kth-largest-element-heap-explained-finding-5-in-3-2-1-5-6-4/diagrams/hero.svg)
Learn how to find the 2nd largest element in [3, 2, 1, 5, 6, 4] using a min-heap window model. Master $O(N \log k)$ tracking without sorting the whole array.
![Rooms for [[0,30],[5,10],[15,20]] overview diagram](/blogs/meeting-rooms-ii-min-rooms-explained-rooms-for-0-30-5-10-15-20/diagrams/hero.svg)
Learn Meeting Rooms II (Min Rooms) by tracing [[0,30],[5,10],[15,20]]. Master interval overlaps and min-heap allocation through a clear mental model.
![Merge [[1,3],[2,6],[8,10],[15,18]] and [[1,4],[4,5]] overview diagram](/blogs/merge-overlapping-intervals-explained-tracing-1-3-2-6/diagrams/hero.svg)
Master interval merging through mental models. Trace [[1,3],[2,6],[8,10],[15,18]] step-by-step and learn how sorting unlocks linear-time solutions.
![Triplets in [-1, 0, 1, 2, -1, -4] overview diagram](/blogs/3sum-with-duplicate-skipping-explained-tracing-1-0-1-2-1-4/diagrams/hero.svg)
Learn 3Sum with duplicate skipping by tracing [-1, 0, 1, 2, -1, -4] step-by-step. Build a rock-solid mental model of sorting and two-pointer traversal.
![Top 2 frequent in [1, 1, 1, 2, 2, 3] overview diagram](/blogs/top-k-frequent-elements-explained-finding-top-2-in-1-1-1-2-2-3/diagrams/hero.svg)
Master the Top K frequent elements pattern by tracing how to find the top 2 elements in [1, 1, 1, 2, 2, 3] using frequency maps and bucket sort.
