Coding interview preparation by programming language

JavaScript coding interview preparation

Practice the data structures, language behavior, asynchronous utilities, and testing habits that support clear JavaScript interview solutions.

Debounce vs. throttle in JavaScript

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

Implement Promise.all in JavaScript

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

The JavaScript event loop, explained with execution traces

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

Interactive tools

Debounce and throttle visualizer

Send events and compare immediate, debounced, and throttled callbacks. Adjust the wait and leading/trailing options and inspect exact timelines.

Topics

JavaScript interview utilities and concepts

Practice promises, closures, array methods, event emitters, debounce, and throttle with guides and coding lessons.

Implement a JavaScript queue for BFS without repeated shift calls

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

Interactive tools

JavaScript output quiz: 12 snippets with explained answers

Predict JavaScript output for closures, this, copies, Map keys, defaults, sorting, and promises. Compare explanations and retry missed snippets.

Worked lesson walkthroughs

Two Sum in JavaScript: return every matching index pair

Solve the all-pairs Two Sum exercise with a JavaScript Map. Trace complement lookups, handle index zero, preserve indexes, and test numeric assumptions.

Valid brackets in JavaScript: a stack that ignores ordinary text

Validate nested parentheses, brackets, and braces with a JavaScript array stack. Trace mismatched closers, ignore other characters, and test nesting and empty input.

Product of array except self in JavaScript without division

Build the product array with prefix and suffix passes in JavaScript. Trace the output in place, handle zeros, avoid fill aliasing mistakes, and explain numeric limits.

TypeScript

TypeScript coding interview preparation

Use precise types for maps, trees, unions, and asynchronous functions while keeping your interview implementation readable and testable.

TypeScript collections: missing values, keys, and readonly contracts

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

Python

Python coding interview preparation

Choose lists, dictionaries, sets, deque, and heaps deliberately. Practice readable Python solutions with clear time and memory analysis.

Reference

Python collections for interviews: dict, Counter, deque, and heapq

Choose Python collections by operation, write counts and adjacency lists, and test queue, heap, missing-key, and copying behavior.

Count islands in Python with iterative flood fill

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

Worked lesson walkthroughs

Two Sum in Python: all index pairs with a dictionary

Use enumerate and a dictionary to return every matching pair of indexes. Follow the invariant, distinguish missing keys from index zero, and test the unique-integer contract.

Valid brackets in Python: matching delimiters with a list stack

Write a Python bracket validator using append, pop, and a closer-to-opener dictionary. Follow a nesting trace and test text, missing openers, and crossing brackets.

Product of array except self in Python: two passes, no division

Solve Product Array using Python lists and running prefix and suffix products. Explain the invariant, zeros, negative numbers, and the cost of large integer arithmetic.

Java

Java coding interview preparation: collections, numbers, and traversal

Prepare with HashMap, ArrayDeque, safe comparators, UTF-16 text, and tested Java implementations of Two Sum and graph traversal.

Java PriorityQueue: top-K values, comparators, and stable ties

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

Worked lesson walkthroughs

Two Sum in Java: all index pairs with HashMap

Build a Java HashMap solution for every matching index pair. Handle Integer null checks, avoid complement overflow, and convert the result to int[][] with tests.

Valid brackets in Java: ArrayDeque and ordered matching

Use ArrayDeque as a stack to validate brackets in Java. Handle pop safely, choose character types, ignore ordinary text, and verify a complete set of edge cases.

Product of array except self in Java with long arrays

Implement prefix and suffix products with long[] in Java. Initialize the output correctly, handle zeros without division, and state the overflow assumptions with tests.

C++

C++ coding interview preparation: STL, ownership, and boundaries

Use vectors, hash maps, queues, and priority queues while handling iterator invalidation, integer overflow, and safe index boundaries.

C++ lower_bound and upper_bound: counts, neighbors, and record ranges

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

Go

Go coding interview preparation: slices, maps, and text

Practice Go slice ownership, map presence checks, byte and rune boundaries, and queue-based graph traversal with worked code.

Longest unique substring in Go: bytes, runes, and Unicode

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

Rust

Rust coding interview preparation: borrowing and collections

Write interview algorithms with borrowed slices, explicit Option results, HashMap entries, VecDeque, and min-heap priority through Reverse.

Rust BFS shortest paths with borrowed graph labels

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

C#

C# coding interview preparation: collections, tuples, and traversal

Practice C# dictionary presence, nullable tuple results, widened arithmetic, queue traversal, priority ordering, and UTF-16 text contracts.

Kotlin

Kotlin coding interview preparation: arrays, nullability, and JVM collections

Use primitive arrays, nullable results, map presence, JVM queues, safe comparisons, and explicit collection-sharing assumptions in Kotlin.

Swift