GyanDev Deep technical notes for modern developers. https://gyandev.org/ 2026-04-24T00:00:00.000Z Sonu Shahuji Heaps & Priority Queues https://gyandev.org/courses/dsa/ 2026-04-24T00:00:00.000Z 2026-04-24T00:00:00.000Z Sonu Shahuji Pattern-first mastery of heap problems — the complete-binary-tree mental model, canonical templates, and 16 FAANG-grade patterns in Python and TypeScript. Frequency-based https://gyandev.org/courses/dsa/heaps 2026-04-24T00:00:00.000Z 2026-04-24T00:00:00.000Z Sonu Shahuji Heap ordered by counts — top-K elements by frequency or reorderings that respect frequency caps. Frequency Sort https://gyandev.org/courses/dsa/heaps/frequency-based 2026-04-24T00:00:00.000Z 2026-04-24T00:00:00.000Z Sonu Shahuji Sort array elements by descending frequency — count with a hash map, then pop from an uncapped max-heap and emit each value that many times. Top K Frequent Elements https://gyandev.org/courses/dsa/heaps/frequency-based 2026-04-24T00:00:00.000Z 2026-04-24T00:00:00.000Z Sonu Shahuji Return the K most frequently occurring values in an array — count with a hash map, then Top-K with a min-heap keyed on frequency. Heaps — Fundamentals https://gyandev.org/courses/dsa/heaps 2026-04-24T00:00:00.000Z 2026-04-24T00:00:00.000Z Sonu Shahuji Foundations of binary heaps and priority queues — index arithmetic, operations, recognition signals, and the five templates that unlock every heap problem. Greedy Combine https://gyandev.org/courses/dsa/heaps 2026-04-24T00:00:00.000Z 2026-04-24T00:00:00.000Z Sonu Shahuji Repeatedly extract the two smallest, combine, and reinsert — Huffman-style accumulation. Connect Ropes with Minimum Cost https://gyandev.org/courses/dsa/heaps/greedy-combine 2026-04-24T00:00:00.000Z 2026-04-24T00:00:00.000Z Sonu Shahuji Repeatedly merge the two shortest ropes into one — a Huffman-style greedy that minimises total joining cost using a min-heap. K-way Merge https://gyandev.org/courses/dsa/heaps 2026-04-24T00:00:00.000Z 2026-04-24T00:00:00.000Z Sonu Shahuji Merge K sorted sequences or matrix cells by maintaining a heap of active heads. Kth Smallest in Sorted Matrix https://gyandev.org/courses/dsa/heaps/k-way-merge 2026-04-24T00:00:00.000Z 2026-04-24T00:00:00.000Z Sonu Shahuji Find the K-th smallest value in a row- and column-sorted matrix by treating rows as K sorted lists and applying the K-way merge template. Merge K Sorted Lists https://gyandev.org/courses/dsa/heaps/k-way-merge 2026-04-24T00:00:00.000Z 2026-04-24T00:00:00.000Z Sonu Shahuji Merge K sorted linked lists or arrays into one sorted output using a min-heap seeded with the head of each source — the canonical K-way merge. Scheduling with Heap https://gyandev.org/courses/dsa/heaps 2026-04-24T00:00:00.000Z 2026-04-24T00:00:00.000Z Sonu Shahuji Greedy task/interval picks driven by a priority queue — cooldowns, deadlines, room assignment. Maximum Beauty with Deadlines https://gyandev.org/courses/dsa/heaps/scheduling-with-heap 2026-04-24T00:00:00.000Z 2026-04-24T00:00:00.000Z Sonu Shahuji Maximise total beauty of toys sold within per-toy deadlines — sort by deadline, then use a min-heap as capacity-bounded beauty tracker. Meeting Rooms II (Heap) https://gyandev.org/courses/dsa/heaps/scheduling-with-heap 2026-04-24T00:00:00.000Z 2026-04-24T00:00:00.000Z Sonu Shahuji Find the minimum conference rooms needed for a meeting list — sort by start, keep end-times in a min-heap, reuse the earliest-free room. Reorganize String https://gyandev.org/courses/dsa/heaps/scheduling-with-heap 2026-04-24T00:00:00.000Z 2026-04-24T00:00:00.000Z Sonu Shahuji Rearrange a string so no two adjacent characters are equal by greedily emitting the most-frequent available character and deferring the one just used. Task Scheduler https://gyandev.org/courses/dsa/heaps/scheduling-with-heap 2026-04-24T00:00:00.000Z 2026-04-24T00:00:00.000Z Sonu Shahuji Compute the minimum CPU cycles to finish a task list with a same-task cooldown using a max-heap of remaining counts plus a cooldown queue. Top K Selection https://gyandev.org/courses/dsa/heaps 2026-04-24T00:00:00.000Z 2026-04-24T00:00:00.000Z Sonu Shahuji Bounded-size heap + linear scan. Opposite-polarity rule: min-heap for K-largest, max-heap for K-smallest. K Closest Elements to X https://gyandev.org/courses/dsa/heaps/top-k-selection 2026-04-24T00:00:00.000Z 2026-04-24T00:00:00.000Z Sonu Shahuji Return the K values closest to target X by absolute difference using a size-K max-heap keyed on distance. K Closest Points to Origin https://gyandev.org/courses/dsa/heaps/top-k-selection 2026-04-24T00:00:00.000Z 2026-04-24T00:00:00.000Z Sonu Shahuji Find the K points closest to (0, 0) using a size-K max-heap on squared Euclidean distance — no sqrt required. Kth Largest Element https://gyandev.org/courses/dsa/heaps/top-k-selection 2026-04-24T00:00:00.000Z 2026-04-24T00:00:00.000Z Sonu Shahuji Find the K-th largest element in an unsorted array using a bounded min-heap of size K — the canonical Top-K template. Kth Smallest Element https://gyandev.org/courses/dsa/heaps/top-k-selection 2026-04-24T00:00:00.000Z 2026-04-24T00:00:00.000Z Sonu Shahuji Find the K-th smallest element in an unsorted array with a bounded max-heap of size K — the mirror of the K-th largest template.