The 15 Topics
1. Language Fundamentals & Memory ModelCovers integer overflow, float precision, equality semantics, hashCode/equals contracts, copy semantics, and memory-management mechanics.2. Arrays & Dynamic ArraysHow each language allocates, grows, copies, and mutates arrays/lists — fixed vs. dynamic sizing, aliasing traps, and sort-mutation gotchas.3. Strings & Text ProcessingHow each language builds, copies, indexes, and compares immutable strings efficiently — concatenation cost, interning, and UTF-16 traps.4. Hash Maps & Hash SetsCovers custom-key hashing, insertion-order guarantees, default-value idioms, safe iteration-while-mutating, and sorted-map alternatives.5. Stacks, Queues & DequesPicking the right stack/queue/deque type per language and dodging the shift/unshift O(n) trap that silently breaks complexity.6. Heaps & Priority QueuesHow to build, max-flip, and tie-break a heap in each language — and hand-rolling one entirely from scratch in JavaScript.7. Linked ListsHand-rolling node classes and pointer-rewiring idioms, plus the identity-comparison and recursion-depth pitfalls that trip up traversal.8. Trees & Recursion MechanicsHow deep you can recurse before each runtime crashes, and the null-check, default-argument, and multi-return idioms tree recursion depends on.9. TriesHand-rolling trie nodes from scratch — dict/HashMap/array child storage, end-of-word flags, and per-node memory overhead.10. GraphsConstructing adjacency lists from edge lists, hashed-vs-dense visited tracking, and BFS/DFS queue-and-stack plumbing by hand.11. Backtracking MechanicsThe choose-explore-unchoose cycle: mutable push/pop undo, copying results at the leaf, and each language's recursion-depth ceiling.12. Sorting & Custom ComparatorsSorting by key vs. hand-written comparator, chaining multi-field tiebreakers, and dodging JS's default lexicographic-sort trap.13. DP Memoization PatternsWiring up recursive memoization caches, encoding multi-param keys, and avoiding DP-table aliasing and recursion-depth bugs.14. Bit Manipulation & Numeric Edge CasesHandling fixed-width overflow, 32-bit coercion, modulo/division sign rules, and bit-counting helpers correctly in each runtime's numeric model.15. Union-Find BoilerplateHand-rolling the array-based parent/rank union-find structure: initialization, iterative path compression, and union-by-rank, since none ship one built in.