12 — Priority Queue

Priority queue as an abstract interface — insert with a priority, extract the highest-priority item — and why a binary heap, not a sorted list or a balanced BST, is usually the implementation of choice; includes full top-K and k-way merge worked examples.

Data Structures & Algorithms

A book-shaped table of contents for MAANG-interview DSA prep: Python language foundations, mathematical and algorithmic foundations, arrays/strings, linked structures, stacks/queues, trees, graphs, sorting/searching, dynamic programming, greedy algorithms, backtracking, bit manipulation, advanced data structures, advanced algorithms, interview problem patterns, and MAANG interview mastery — a book-length progression from fundamentals to Google/Meta/Amazon/Apple/Netflix/Microsoft (L4–L6) interview readiness.

1 — Two Pointers Pattern

Recognizing when a problem's brute-force nested loop collapses to a single pass with two coordinated pointers.

10 — BFS Pattern

Recognizing shortest-path/level-order/minimum-step problems that breadth-first search solves optimally on unweighted graphs.

11 — Tree DFS Pattern

Recognizing tree problems that reduce to a DFS template carrying a small amount of state root-to-leaf.

12 — Graph Pattern

Recognizing problems phrased as text/grid/relationship data that are actually graph traversal or connectivity in disguise.