Representative Enumeration problems
Count all prime numbers less than a given integer n using efficient array and math-based enumeration techniques.
Open problem page#479 Largest Palindrome ProductFind the largest palindromic number from the product of two n-digit integers using math and enumeration efficiently.
Open problem page#816 Ambiguous CoordinatesFind all valid 2D coordinate possibilities for an ambiguous input string using backtracking and pruning techniques.
Open problem page#829 Consecutive Numbers SumFind the number of ways to express a number as the sum of consecutive positive integers.
Open problem page#845 Longest Mountain in ArrayFind the length of the longest subarray forming a mountain pattern using state transitions and two-pointer logic efficiently.
Open problem page#869 Reordered Power of 2Determine if a number's digits can be rearranged to form a power of two using counting and hash-based checks.
Open problem page#906 Super PalindromesCount all super-palindromes in a given numeric range, where each is a palindrome and square of a palindrome.
Open problem page#949 Largest Time for Given DigitsGiven four digits, determine the latest valid 24-hour time possible using each digit exactly once with backtracking.
Open problem page#970 Powerful IntegersFind all integers that can be expressed as x^i + y^j up to a given bound using a Hash Table plus Math approach.
Open problem pageEnumeration interview questions usually collapse into a small set of repeatable moves. This page groups those GhostInterview problem pages together so you can stay inside one pattern family, compare representative questions, and practice explanations that transfer across multiple prompts. If you are trying to sharpen one interview weakness instead of browsing the entire library, start here.
Why Enumeration Matters In Coding Interviews
Interviewers rarely care about the label alone. They care about whether you can recognize when the Enumeration pattern applies, explain why it applies, and avoid the failure modes that usually show up under time pressure. That is why this page focuses on the family of problems rather than a single isolated example.
Pattern families that show up here
- Array scanning plus hash lookup
- Math plus Enumeration
- Backtracking search with pruning
Use this page to narrow the session
Start from this topic hub, choose one or two representative problems, and then open the detailed problem pages only after you know which version of the pattern you want to reinforce.
How To Practice This Topic
The best workflow is to keep the prep block narrow. Pick one easy or medium problem to confirm the base pattern, then one medium or hard problem to test whether the explanation still holds when the constraints tighten. Once the logic is stable, move into GhostInterview to rehearse the live explanation flow.
Focus on transfer, not title count
Solving more Enumeration titles is less useful than understanding how the same move changes across examples. Try to describe what stays the same and what changes from one problem to the next.
Use the problem page when you want the exact breakdown
This topic hub is the discovery layer. The single-problem pages are where you get the answer-first summary, examples, constraints, approach, complexity, pitfalls, and solver CTA.
How GhostInterview Fits
GhostInterview works best after you know which pattern family you are inside. Use this page to choose the right Enumeration problem, then use the solver to get the answer path, complexity framing, and follow-up support without switching into a generic study flow.
FAQ
What does the Enumeration topic usually test in interviews?
Enumeration questions usually test whether you can spot the underlying pattern quickly, explain the trade-offs, and move from intuition to implementation without losing clarity.
How should I use this Enumeration topic page?
Use it as a pattern hub. Start with the representative problems on this page, compare the common approach, and then open the exact problem page when you want the full breakdown.
How many GhostInterview problem pages are in the Enumeration group?
This topic page currently groups 118 indexed GhostInterview problem pages under the Enumeration family.
Should I practice this topic before harder patterns?
That depends on your current gaps. If Enumeration is already a weak spot in interviews, it is usually better to stabilize it first before moving into more advanced or less frequent patterns.
Where does GhostInterview fit once I pick a Enumeration problem?
The topic page narrows the pattern family. The problem page gives the exact breakdown. GhostInterview is the solver layer when you need direct help with execution, complexity, and follow-up handling.
Stay close to the same reasoning family
Need direct help once you choose a Enumeration problem?
Use GhostInterview as the solver layer after you select the exact prompt. Capture the question, get the answer path and complexity framing, and keep the workflow inside the same topic family.