The Heap Data Structure: The Priority Queue That's Everywhere

Every job scheduler, every event loop, every Dijkstra implementation, every top-K query, every kernel timer wheel -- they all use a heap. The data structure is so simple it fits in 30 lines of code, so fast it does insertions and deletions in O(log n), and so common that 'priority queue' and 'heap' are nearly synonymous in practice. Knowing it changes how you think about scheduling problems.