Enumeration is a problem-solving technique where you systematically generate and evaluate all possible candidates to find those that satisfy a given condition. In coding interviews, enumeration is often used as the starting point for solving complex problems because it guarantees correctness before optimizations are applied.
Many interview questions initially appear difficult but become manageable once you think in terms of enumerating possibilities—subsets, permutations, pairs, or combinations. For example, you might enumerate all subsets of an array, all possible paths in a grid, or all valid configurations of a structure. Although the naive approach can be expensive, enumeration frequently leads to insights that allow improvements using techniques like Backtracking, Bitmask, or efficient recursion strategies.
Common enumeration patterns include:
Mastering enumeration helps you build strong problem-solving intuition. Once you understand how to explore the full solution space safely and efficiently, you can gradually optimize with pruning, mathematical insights, or better data structures.
On this page, you'll find 95 carefully selected enumeration problems designed to strengthen your brute-force reasoning and help you recognize when enumeration is the right tool during coding interviews.
Many enumeration problems involve iterating through elements, pairs, or subsets within arrays.
Bitmasking enables efficient enumeration of subsets and combinations using binary representations.
Recursion is commonly used to explore and generate all possible configurations in enumeration problems.
Backtracking improves enumeration by pruning invalid branches and avoiding unnecessary exploration.
Start Easy, progress to Hard.
Frequently appear alongside Enumeration.
Common questions about Enumeration.
Enumeration is a form of brute-force approach, but it is usually more structured. Instead of randomly trying possibilities, enumeration carefully generates candidates in a logical and systematic order.
Enumeration can be optimized using pruning techniques like backtracking, bitmasking, or mathematical insights. Efficient data structures and early stopping conditions also reduce unnecessary checks.
Use enumeration when the search space is small enough or when you need a correct baseline solution. It is also useful for discovering patterns that lead to optimized solutions.
Enumeration is a technique where you systematically generate all possible candidates and check which ones satisfy the problem constraints. It is often used as a brute-force baseline before applying optimizations.
Practicing 50–100 problems is usually enough to recognize common enumeration patterns. Solving a diverse set helps you quickly decide when enumeration is feasible and when optimization is needed.