Learn and practice

Guides

Worked explanations of interview problems, JavaScript behavior, and algorithm choices. Read the reasoning, inspect the code, and move into practice.

Build both functions, compare leading and trailing calls, and test timing behavior with an interactive event timeline.

Write a Promise.all implementation that preserves input order, handles empty iterables, and rejects correctly.

Trace synchronous code, promise microtasks, timers, and async functions. Work through examples before checking their output.

Compare queues, stacks, shortest paths, visited sets, and memory costs with worked graph and grid examples.

Analyze loops, nested work, recursion, and auxiliary memory. Learn to state assumptions and distinguish worst-case from amortized cost.

A worked Two Sum interview: clarify the contract, develop a baseline, justify a hash map, test edge cases, and explain complexity.

Build a FIFO queue with bounded compaction, distinguish empty results from undefined values, and use it in a cyclic graph traversal.

Model lookup presence explicitly, handle unchecked indexes, preserve zero and undefined, and write a typed frequency counter and graph BFS.

Solve a four-neighbor binary-grid problem with an explicit stack, visited-set and in-place variants, complexity analysis, and boundary tests.

Retain top-K stream values, process jobs with explicit tie order, and test Java heap ranking separately from iteration and sorted output.

Use C++ search boundaries for duplicate counts, strict predecessors and successors, and custom record keys without invalid iterator operations.

Implement rune and ASCII sliding windows, reject invalid input, preserve forward-only boundaries, and test Unicode length assumptions.

Return a shortest unweighted route using borrowed string labels, a FIFO frontier, explicit parents, and a lifetime that matches the source graph.