Coding interviews can be intimidating with the wide range of algorithms and data structures you could be tested on. However, while there are countless concepts you could study, just mastering a core set of the most common patterns will prepare you for a majority of questions.
Based on extensive interview experience, these 6 concepts represent some of the most frequently tested and high-yield topics to focus your preparation on.
The number one pattern to understand is hash maps. They are by far the most commonly used data structure in coding interviews.
Hash maps allow for O(1) or constant time insertion, deletion, and lookup. This makes them invaluable for improving efficiency in so many algorithms. The famous “two sum” problem can be easily solved by using a hash map to store values, rather than brute force nested looping through the array.
Even if the hash map itself doesn’t fully solve a problem, it is very often used as a utility for caching values or accessing data quickly. Given how ubiquitous hash maps are, any interview problem becomes much harder if you aren’t deeply familiar with how they work and just how efficient their operations are.
Recursion is another huge category for coding interviews. Like hash maps, it can be applied broadly across tree traversals, backtracking, graph algorithms, and more.
Many candidates find recursion intimidating at first. But with practice, it becomes second nature. Be sure you understand the base case, recursive step, call stack, and tradeoffs compared to iterative solutions. Many recursive patterns become easy once internalized.
Mastering recursion is key for tackling everything from binary trees to advanced graph algorithms efficiently. It unlocks your ability to reason abstractly about complex problems.
DFS and BFS traversals form the foundation for countless graph algorithms. But they have broad applicability beyond just graphs to problems involving trees, matrices, and other nested data…